CVE-2026-77756 (GCVE-0-2026-77756)

Vulnerability from cvelistv5 – Published: 2026-09-23 11:18 – Updated: 2026-09-23 18:10
VLAI
Title
Apache Tomcat: Transfer-Encoding honored for HTTP/1.0 requests
Summary
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-23 13:18 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
apache CNA under the mitre root
CNA scorecard B 76/100 over 1085 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Apache Software Foundation Apache Tomcat Affected: 11.0.0-M1 , ≤ 11.0.25 (semver)
Affected: 10.1.0-M1 , ≤ 10.1.59 (semver)
Affected: 9.0.47 , ≤ 9.0.121 (semver)
Affected: 8.5.67 , ≤ 8.5.100 (semver)
Unaffected: 0 , ≤ 7.0.109 (semver)
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "HIGH",
              "attackVector": "NETWORK",
              "availabilityImpact": "LOW",
              "baseScore": 3.7,
              "baseSeverity": "LOW",
              "confidentialityImpact": "NONE",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-77756",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-23T13:18:16.430403Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-23T13:18:19.230Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      },
      {
        "providerMetadata": {
          "dateUpdated": "2026-09-23T18:10:42.842Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/09/23/22"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Apache Tomcat",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThanOrEqual": "11.0.25",
              "status": "affected",
              "version": "11.0.0-M1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "10.1.59",
              "status": "affected",
              "version": "10.1.0-M1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "9.0.121",
              "status": "affected",
              "version": "9.0.47",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "8.5.100",
              "status": "affected",
              "version": "8.5.67",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.109",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eInconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027) vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy.\u003c/p\u003e\u003cp\u003eThis issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121.\u003c/p\u003e\u003cp\u003eThe following versions were EOL at the time the CVE was created but are \nknown to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected.\u003c/p\u003e\u003cp\u003eUsers are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.\u003c/p\u003e"
            }
          ],
          "value": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027) vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy.\n\n\n\nThis issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121.\n\n\n\nThe following versions were EOL at the time the CVE was created but are \nknown to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected.\n\n\n\nUsers are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "text": "low"
            },
            "type": "Textual description of severity"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-444",
              "description": "CWE-444 Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-23T11:18:02.672Z",
        "orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
        "shortName": "apache"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://lists.apache.org/thread/bl5b6rxqh3vb2k9bj2794vhor7o6xl3z"
        }
      ],
      "source": {
        "discovery": "INTERNAL"
      },
      "title": "Apache Tomcat: Transfer-Encoding honored for HTTP/1.0 requests",
      "x_generator": {
        "engine": "Vulnogram 0.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
    "assignerShortName": "apache",
    "cveId": "CVE-2026-77756",
    "datePublished": "2026-09-23T11:18:02.672Z",
    "dateReserved": "2026-08-21T09:55:42.227Z",
    "dateUpdated": "2026-09-23T18:10:42.842Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-77756",
      "date": "2026-10-28",
      "epss": "0.00526",
      "percentile": "0.44442"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "defaultStatus": "unaffected",
                "product": "Apache Tomcat",
                "vendor": "Apache Software Foundation",
                "versions": [
                  {
                    "lessThanOrEqual": "11.0.25",
                    "status": "affected",
                    "version": "11.0.0-M1",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "10.1.59",
                    "status": "affected",
                    "version": "10.1.0-M1",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "9.0.121",
                    "status": "affected",
                    "version": "9.0.47",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "8.5.100",
                    "status": "affected",
                    "version": "8.5.67",
                    "versionType": "semver"
                  },
                  {
                    "lessThanOrEqual": "7.0.109",
                    "status": "unaffected",
                    "version": "0",
                    "versionType": "semver"
                  }
                ]
              }
            ],
            "source": "security@apache.org"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027) vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy.\n\n\n\nThis issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121.\n\n\n\nThe following versions were EOL at the time the CVE was created but are \nknown to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected.\n\n\n\nUsers are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue."
          }
        ],
        "id": "CVE-2026-77756",
        "lastModified": "2026-09-23T19:19:18.720",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "LOW",
                "baseScore": 3.7,
                "baseSeverity": "LOW",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 2.2,
              "impactScore": 1.4,
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-77756",
                "options": [
                  {
                    "exploitation": "none"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-23T13:18:16.430403Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-09-23T12:17:06.663",
        "references": [
          {
            "source": "security@apache.org",
            "url": "https://lists.apache.org/thread/bl5b6rxqh3vb2k9bj2794vhor7o6xl3z"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "http://www.openwall.com/lists/oss-security/2026/09/23/22"
          }
        ],
        "sourceIdentifier": "security@apache.org",
        "vulnStatus": "Awaiting Analysis",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-444"
              }
            ],
            "source": "security@apache.org",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-10-08T04:16:10+00:00",
      "cve": "CVE-2026-77756",
      "id": "CVE-2026-77756",
      "initial_release_date": "2026-09-23T11:18:02.672000+00:00",
      "product_status:fixed": "42",
      "product_status:known_affected": "87",
      "product_status:known_not_affected": "4",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "tomcat: Apache Tomcat: Request smuggling vulnerability can lead to denial of service",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-77756.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "providerMetadata": {
              "dateUpdated": "2026-09-23T18:10:42.842Z",
              "orgId": "af854a3a-2127-422b-91ae-364da2661108",
              "shortName": "CVE"
            },
            "references": [
              {
                "url": "http://www.openwall.com/lists/oss-security/2026/09/23/22"
              }
            ],
            "title": "CVE Program Container"
          },
          {
            "metrics": [
              {
                "cvssV3_1": {
                  "attackComplexity": "HIGH",
                  "attackVector": "NETWORK",
                  "availabilityImpact": "LOW",
                  "baseScore": 3.7,
                  "baseSeverity": "LOW",
                  "confidentialityImpact": "NONE",
                  "integrityImpact": "NONE",
                  "privilegesRequired": "NONE",
                  "scope": "UNCHANGED",
                  "userInteraction": "NONE",
                  "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
                  "version": "3.1"
                }
              },
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-77756",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-09-23T13:18:16.430403Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-09-23T13:18:12.690Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Apache Tomcat",
              "vendor": "Apache Software Foundation",
              "versions": [
                {
                  "lessThanOrEqual": "11.0.25",
                  "status": "affected",
                  "version": "11.0.0-M1",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "10.1.59",
                  "status": "affected",
                  "version": "10.1.0-M1",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "9.0.121",
                  "status": "affected",
                  "version": "9.0.47",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "8.5.100",
                  "status": "affected",
                  "version": "8.5.67",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "7.0.109",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cp\u003eInconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027) vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy.\u003c/p\u003e\u003cp\u003eThis issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121.\u003c/p\u003e\u003cp\u003eThe following versions were EOL at the time the CVE was created but are \nknown to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected.\u003c/p\u003e\u003cp\u003eUsers are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.\u003c/p\u003e"
                }
              ],
              "value": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027) vulnerability in Apache Tomcat caused by processing the transfer-encoding header for an HTTP/1.0 request may allow an attacker to cause one request from another user to fail when Tomcat is located behind a reverse proxy.\n\n\n\nThis issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.47 through 9.0.121.\n\n\n\nThe following versions were EOL at the time the CVE was created but are \nknown to be affected: from 8.5.67 through 8.5.100. Other unsupported versions may also be affected.\n\n\n\nUsers are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue."
            }
          ],
          "metrics": [
            {
              "other": {
                "content": {
                  "text": "low"
                },
                "type": "Textual description of severity"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-444",
                  "description": "CWE-444 Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-09-23T11:18:02.672Z",
            "orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
            "shortName": "apache"
          },
          "references": [
            {
              "tags": [
                "vendor-advisory"
              ],
              "url": "https://lists.apache.org/thread/bl5b6rxqh3vb2k9bj2794vhor7o6xl3z"
            }
          ],
          "source": {
            "discovery": "INTERNAL"
          },
          "title": "Apache Tomcat: Transfer-Encoding honored for HTTP/1.0 requests",
          "x_generator": {
            "engine": "Vulnogram 0.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
        "assignerShortName": "apache",
        "cveId": "CVE-2026-77756",
        "datePublished": "2026-09-23T11:18:02.672Z",
        "dateReserved": "2026-08-21T09:55:42.227Z",
        "dateUpdated": "2026-09-23T18:10:42.842Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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

JSON

Loading timeline…




    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.