Vulnerability-Lookup

RHSA-2026:91583

Vulnerability from csaf_redhat - Published: 2026-10-28 06:54 - Updated: 2026-10-29 07:14

Summary

Red Hat Security Advisory: python-tornado security update

Severity

Important

Notes

Topic: An update for python-tornado is now available for Red Hat Enterprise Linux 10.0 Extended Update Support. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Details: Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems. Security Fix(es): * tornado: Tornado: Denial of Service via decompression bomb in CurlAsyncHTTPClient (CVE-2026-103262) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.

CVE-2026-103262

A flaw was found in Tornado. A remote malicious server can cause a Denial of Service (DoS) when an application using the CurlAsyncHTTPClient component fetches an untrusted web address. Because the client fails to enforce limits on incoming response sizes, the attacker can return a small, highly compressed payload (a decompression bomb) that expands to an enormous size. This unbounded memory consumption exhausts system resources and crashes the application.

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)

Affected products

Fixed 13 products

Product	Version	Remediation
Unresolved product id: AppStream-10.0.Z.E2S:python-tornado-0:6.5.10-0.el10_0.1.src	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64	—	Vendor Fix fix Workaround

Threats

Impact Important

References

11 references

URL	Category
https://access.redhat.com/errata/RHSA-2026:91583	self
https://access.redhat.com/security/updates/classi…	external
https://bugzilla.redhat.com/show_bug.cgi?id=2544534	external
https://security.access.redhat.com/data/csaf/v2/a…	self
https://access.redhat.com/security/cve/CVE-2026-103262	self
https://bugzilla.redhat.com/show_bug.cgi?id=2544534	external
https://www.cve.org/CVERecord?id=CVE-2026-103262	external
https://nvd.nist.gov/vuln/detail/CVE-2026-103262	external
https://github.com/tornadoweb/tornado/commit/e412…	external
https://github.com/tornadoweb/tornado/security/ad…	external
https://www.vulncheck.com/advisories/tornado-befo…	external

JSON

To clipboard

{
  "document": {
    "aggregate_severity": {
      "namespace": "https://access.redhat.com/security/updates/classification/",
      "text": "Important"
    },
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Copyright \u00a9 Red Hat, Inc. All rights reserved.",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en",
    "notes": [
      {
        "category": "summary",
        "text": "An update for python-tornado is now available for Red Hat Enterprise Linux 10.0 Extended Update Support.\n\nRed Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.",
        "title": "Topic"
      },
      {
        "category": "general",
        "text": "Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems.\n\nSecurity Fix(es):\n\n* tornado: Tornado: Denial of Service via decompression bomb in CurlAsyncHTTPClient (CVE-2026-103262)\n\nFor more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.",
        "title": "Details"
      },
      {
        "category": "legal_disclaimer",
        "text": "This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.",
        "title": "Terms of Use"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "https://access.redhat.com/security/team/contact/",
      "issuing_authority": "Red Hat Product Security is responsible for vulnerability handling across all Red Hat products and services.",
      "name": "Red Hat Product Security",
      "namespace": "https://www.redhat.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "https://access.redhat.com/errata/RHSA-2026:91583",
        "url": "https://access.redhat.com/errata/RHSA-2026:91583"
      },
      {
        "category": "external",
        "summary": "https://access.redhat.com/security/updates/classification/#important",
        "url": "https://access.redhat.com/security/updates/classification/#important"
      },
      {
        "category": "external",
        "summary": "2544534",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2544534"
      },
      {
        "category": "self",
        "summary": "Canonical URL",
        "url": "https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_91583.json"
      }
    ],
    "title": "Red Hat Security Advisory: python-tornado security update",
    "tracking": {
      "current_release_date": "2026-10-29T07:14:56+00:00",
      "generator": {
        "date": "2026-10-29T07:14:56+00:00",
        "engine": {
          "name": "Red Hat SDEngine",
          "version": "5.4.3"
        }
      },
      "id": "RHSA-2026:91583",
      "initial_release_date": "2026-10-28T06:54:13+00:00",
      "revision_history": [
        {
          "date": "2026-10-28T06:54:13+00:00",
          "number": "1",
          "summary": "Initial version"
        },
        {
          "date": "2026-10-28T06:54:13+00:00",
          "number": "2",
          "summary": "Last updated version"
        },
        {
          "date": "2026-10-29T07:14:56+00:00",
          "number": "3",
          "summary": "Last generated version"
        }
      ],
      "status": "final",
      "version": "3"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_name",
                "name": "Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
                "product": {
                  "name": "Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
                  "product_id": "AppStream-10.0.Z.E2S",
                  "product_identification_helper": {
                    "cpe": "cpe:/o:redhat:enterprise_linux_eus:10.0"
                  }
                }
              }
            ],
            "category": "product_family",
            "name": "Red Hat Enterprise Linux"
          },
          {
            "branches": [
              {
                "category": "product_version",
                "name": "python-tornado-0:6.5.10-0.el10_0.1.src",
                "product": {
                  "name": "python-tornado-0:6.5.10-0.el10_0.1.src",
                  "product_id": "python-tornado-0:6.5.10-0.el10_0.1.src",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python-tornado@6.5.10-0.el10_0.1?arch=src"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "src"
          },
          {
            "branches": [
              {
                "category": "product_version",
                "name": "python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
                "product": {
                  "name": "python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
                  "product_id": "python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado@6.5.10-0.el10_0.1?arch=aarch64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
                "product": {
                  "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
                  "product_id": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python-tornado-debugsource@6.5.10-0.el10_0.1?arch=aarch64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
                "product": {
                  "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
                  "product_id": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado-debuginfo@6.5.10-0.el10_0.1?arch=aarch64"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "aarch64"
          },
          {
            "branches": [
              {
                "category": "product_version",
                "name": "python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
                "product": {
                  "name": "python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
                  "product_id": "python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado@6.5.10-0.el10_0.1?arch=ppc64le"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
                "product": {
                  "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
                  "product_id": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python-tornado-debugsource@6.5.10-0.el10_0.1?arch=ppc64le"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
                "product": {
                  "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
                  "product_id": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado-debuginfo@6.5.10-0.el10_0.1?arch=ppc64le"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "ppc64le"
          },
          {
            "branches": [
              {
                "category": "product_version",
                "name": "python3-tornado-0:6.5.10-0.el10_0.1.s390x",
                "product": {
                  "name": "python3-tornado-0:6.5.10-0.el10_0.1.s390x",
                  "product_id": "python3-tornado-0:6.5.10-0.el10_0.1.s390x",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado@6.5.10-0.el10_0.1?arch=s390x"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
                "product": {
                  "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
                  "product_id": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python-tornado-debugsource@6.5.10-0.el10_0.1?arch=s390x"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
                "product": {
                  "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
                  "product_id": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado-debuginfo@6.5.10-0.el10_0.1?arch=s390x"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "s390x"
          },
          {
            "branches": [
              {
                "category": "product_version",
                "name": "python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
                "product": {
                  "name": "python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
                  "product_id": "python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado@6.5.10-0.el10_0.1?arch=x86_64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
                "product": {
                  "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
                  "product_id": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python-tornado-debugsource@6.5.10-0.el10_0.1?arch=x86_64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64",
                "product": {
                  "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64",
                  "product_id": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64",
                  "product_identification_helper": {
                    "purl": "pkg:rpm/redhat/python3-tornado-debuginfo@6.5.10-0.el10_0.1?arch=x86_64"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "x86_64"
          }
        ],
        "category": "vendor",
        "name": "Red Hat"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python-tornado-0:6.5.10-0.el10_0.1.src as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python-tornado-0:6.5.10-0.el10_0.1.src"
        },
        "product_reference": "python-tornado-0:6.5.10-0.el10_0.1.src",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64"
        },
        "product_reference": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le"
        },
        "product_reference": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x"
        },
        "product_reference": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64"
        },
        "product_reference": "python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-0:6.5.10-0.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.aarch64"
        },
        "product_reference": "python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-0:6.5.10-0.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.ppc64le"
        },
        "product_reference": "python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-0:6.5.10-0.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.s390x"
        },
        "product_reference": "python3-tornado-0:6.5.10-0.el10_0.1.s390x",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-0:6.5.10-0.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.x86_64"
        },
        "product_reference": "python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64"
        },
        "product_reference": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le"
        },
        "product_reference": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x"
        },
        "product_reference": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v. 10.0)",
          "product_id": "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64"
        },
        "product_reference": "python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64",
        "relates_to_product_reference": "AppStream-10.0.Z.E2S"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-103262",
      "cwe": {
        "id": "CWE-409",
        "name": "Improper Handling of Highly Compressed Data (Data Amplification)"
      },
      "discovery_date": "2026-10-01T10:56:14.609538+00:00",
      "ids": [
        {
          "system_name": "Red Hat Bugzilla ID",
          "text": "2544534"
        }
      ],
      "notes": [
        {
          "category": "description",
          "text": "A flaw was found in Tornado. A remote malicious server can cause a Denial of Service (DoS) when an application using the CurlAsyncHTTPClient component fetches an untrusted web address. Because the client fails to enforce limits on incoming response sizes, the attacker can return a small, highly compressed payload (a decompression bomb) that expands to an enormous size. This unbounded memory consumption exhausts system resources and crashes the application.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "tornado: Tornado: Denial of Service via decompression bomb in CurlAsyncHTTPClient",
          "title": "Vulnerability summary"
        },
        {
          "category": "other",
          "text": "This vulnerability has been rated as Important because an untrusted remote server can remotely terminate an application process through memory exhaustion without requiring credentials. By default, Tornado deploys the SimpleAsyncHTTPClient implementation, which includes built-in thresholds for decompressed and raw payload sizes and remains unaffected by this flaw. However, systems that explicitly configure CurlAsyncHTTPClient\u2014typically enabled for custom proxy routing or advanced transport options\u2014bypass these protections and do not enforce body size constraints. When such client applications fetch resources from compromised or malicious web endpoints, the resulting decompression bomb can consume all available system memory, leading to an immediate denial of service.",
          "title": "Statement"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
          "title": "CVSS score applicability"
        }
      ],
      "product_status": {
        "fixed": [
          "AppStream-10.0.Z.E2S:python-tornado-0:6.5.10-0.el10_0.1.src",
          "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
          "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
          "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
          "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
          "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
          "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
          "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.s390x",
          "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
          "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
          "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
          "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
          "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "Canonical URL",
          "url": "https://access.redhat.com/security/cve/CVE-2026-103262"
        },
        {
          "category": "external",
          "summary": "RHBZ#2544534",
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2544534"
        },
        {
          "category": "external",
          "summary": "https://www.cve.org/CVERecord?id=CVE-2026-103262",
          "url": "https://www.cve.org/CVERecord?id=CVE-2026-103262"
        },
        {
          "category": "external",
          "summary": "https://nvd.nist.gov/vuln/detail/CVE-2026-103262",
          "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103262"
        },
        {
          "category": "external",
          "summary": "https://github.com/tornadoweb/tornado/commit/e412435febba4569c552c5c9054f1bf92bd171a9",
          "url": "https://github.com/tornadoweb/tornado/commit/e412435febba4569c552c5c9054f1bf92bd171a9"
        },
        {
          "category": "external",
          "summary": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-chx6-46f5-w4vp",
          "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-chx6-46f5-w4vp"
        },
        {
          "category": "external",
          "summary": "https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-curlasynchttpclient",
          "url": "https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-curlasynchttpclient"
        }
      ],
      "release_date": "2026-10-01T10:42:04.913000+00:00",
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-10-28T06:54:13+00:00",
          "details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\n\nhttps://access.redhat.com/articles/11258",
          "product_ids": [
            "AppStream-10.0.Z.E2S:python-tornado-0:6.5.10-0.el10_0.1.src",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64"
          ],
          "restart_required": {
            "category": "none"
          },
          "url": "https://access.redhat.com/errata/RHSA-2026:91583"
        },
        {
          "category": "workaround",
          "details": "Restrict outbound HTTP client requests to trusted destinations and avoid using the CurlAsyncHTTPClient backend when fetching untrusted web content.\n\n1. Application configuration: Configure Tornado applications to utilize the default SimpleAsyncHTTPClient instead of CurlAsyncHTTPClient, provided specialized libcurl functionality (such as custom proxy configurations or specific TLS options) is not required. The default client enforces strict size boundaries on compressed and uncompressed response bodies.\n2. Network egress filtering: Implement firewall rules or egress network policies to restrict outbound HTTP/HTTPS connections exclusively to verified, trustworthy endpoints, preventing the client from contacting potentially malicious third-party servers.\n3. Operational controls: Ensure that user-supplied or untrusted URLs are validated, sanitized, or rejected before initiating outbound retrieval requests.\n\nCaveats: Switching the HTTP client backend from CurlAsyncHTTPClient to SimpleAsyncHTTPClient may disrupt services that depend on libcurl-specific features. Enforcing egress filtering may block connections to unlisted external services.",
          "product_ids": [
            "AppStream-10.0.Z.E2S:python-tornado-0:6.5.10-0.el10_0.1.src",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "products": [
            "AppStream-10.0.Z.E2S:python-tornado-0:6.5.10-0.el10_0.1.src",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python-tornado-debugsource-0:6.5.10-0.el10_0.1.x86_64",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python3-tornado-0:6.5.10-0.el10_0.1.x86_64",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.aarch64",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.ppc64le",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.s390x",
            "AppStream-10.0.Z.E2S:python3-tornado-debuginfo-0:6.5.10-0.el10_0.1.x86_64"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "tornado: Tornado: Denial of Service via decompression bomb in CurlAsyncHTTPClient"
    }
  ]
}

CVE-2026-103262 (GCVE-0-2026-103262)

Vulnerability from cvelistv5 – Published: 2026-10-01 10:42 – Updated: 2026-10-06 00:08

Title

Tornado before 6.5.9 Denial of Service via CurlAsyncHTTPClient

Summary

Tornado versions before 6.5.9 contain an unbounded memory accumulation vulnerability in CurlAsyncHTTPClient that allows remote attackers to cause denial of service by sending a compressed response. Attackers can send a gzip-encoded decompression bomb that accumulates in memory without size limits, causing the application process to be killed by out-of-memory conditions.

Severity

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-06 00:08 UTC

CWE

CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)

Assigner

VulnCheck CNA under the mitre root

CNA scorecard B 84/100 over 7010 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/tornadoweb/tornado/security/ad…	vendor-advisory
https://github.com/tornadoweb/tornado/commit/e412…	patch
https://www.vulncheck.com/advisories/tornado-befo…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
tornadoweb	tornado	Affected: 0 , < 6.5.9 (semver) Unaffected: 6.5.9 (semver) cpe:2.3:a:tornadoweb:tornado::::::::

Date Public

2026-09-14 00:00

Credits

iaohkut-from-NightWolf-Team aoto-tech

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-103262",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-06T00:08:34.189311Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-06T00:08:58.078Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-chx6-46f5-w4vp"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:pypi/tornado",
          "product": "tornado",
          "vendor": "tornadoweb",
          "versions": [
            {
              "lessThan": "6.5.9",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.5.9",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:tornadoweb:tornado:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.5.9",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "iaohkut-from-NightWolf-Team"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "aoto-tech"
        }
      ],
      "datePublic": "2026-09-14T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "Tornado versions before 6.5.9 contain an unbounded memory accumulation vulnerability in CurlAsyncHTTPClient that allows remote attackers to cause denial of service by sending a compressed response. Attackers can send a gzip-encoded decompression bomb that accumulates in memory without size limits, causing the application process to be killed by out-of-memory conditions."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-409",
              "description": "Improper Handling of Highly Compressed Data (Data Amplification)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-01T10:42:04.913Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "GitHub Security Advisory (GHSA-chx6-46f5-w4vp)",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-chx6-46f5-w4vp"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/tornadoweb/tornado/commit/e412435febba4569c552c5c9054f1bf92bd171a9"
        },
        {
          "name": "VulnCheck Advisory: Tornado before 6.5.9 Denial of Service via CurlAsyncHTTPClient",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-curlasynchttpclient"
        }
      ],
      "title": "Tornado before 6.5.9 Denial of Service via CurlAsyncHTTPClient",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-103262",
    "datePublished": "2026-10-01T10:42:04.913Z",
    "dateReserved": "2026-09-30T10:55:39.869Z",
    "dateUpdated": "2026-10-06T00:08:58.078Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

Publication & reservation Sightings KEV catalogs Other timestamps

Loading timeline…

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted