Vulnerability-Lookup

CVE-2021-29921 (GCVE-0-2021-29921)

Vulnerability from cvelistv5 – Published: 2021-05-06 00:00 – Updated: 2025-11-03 21:44

Summary

In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string. This (in some situations) allows attackers to bypass access control that is based on IP addresses.

Severity

9.8 (Critical)


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

CWE

Assigner

mitre mitre root

References

17 references

URL	Tags
https://github.com/sickcodes
https://docs.python.org/3/library/ipaddress.html
https://github.com/python/cpython/blob/63298930fb…
https://sick.codes/sick-2021-014
https://www.oracle.com//security-alerts/cpujul2021.html
https://github.com/sickcodes/security/blob/master…
https://python-security.readthedocs.io/vuln/ipadd…
https://bugs.python.org/issue36384
https://github.com/python/cpython/pull/12577
https://github.com/python/cpython/pull/25099
https://security.netapp.com/advisory/ntap-2021062…
https://www.oracle.com/security-alerts/cpuoct2021.html
https://www.oracle.com/security-alerts/cpujan2022.html
https://www.oracle.com/security-alerts/cpuapr2022.html
https://www.oracle.com/security-alerts/cpujul2022.html
https://security.gentoo.org/glsa/202305-02	vendor-advisory
https://lists.debian.org/debian-lts-announce/2024…

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      "product_status:fixed": "594",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "python-ipaddress: Improper input validation of octal strings",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-29921.json",
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}

RHSA-2021:3254

Vulnerability from csaf_redhat - Published: 2021-08-24 12:50 - Updated: 2026-08-25 16:56

Summary

Red Hat Security Advisory: rh-python38 security, bug fix, and enhancement update

Severity

Moderate

Scope

17 vulnerabilities in this advisory, including CVE-2021-29921.

CVE-2021-29921

A flaw was found in python-ipaddress. Improper input validation of octal strings in stdlib ipaddress allows unauthenticated remote attackers to perform indeterminate SSRF, RFI, and LFI attacks on many programs that rely on Python stdlib ipaddress. The highest threat from this vulnerability is to data integrity and system availability.

9.1 (Critical)


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

Fixed: 126 products

https://access.redhat.com/errata/RHSA-2021:3254

Open the full advisory

RHSA-2021:4160

Vulnerability from csaf_redhat - Published: 2021-11-09 18:32 - Updated: 2026-08-25 16:57

Summary

Red Hat Security Advisory: python39:3.9 and python39-devel:3.9 security update

Severity

Moderate

Scope

7 vulnerabilities in this advisory, including CVE-2021-29921.

CVE-2021-29921

9.1 (Critical)


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

Fixed: 229 products

https://access.redhat.com/errata/RHSA-2021:4160

Open the full advisory

RHSA-2021:4162

Vulnerability from csaf_redhat - Published: 2021-11-09 17:54 - Updated: 2026-08-25 16:57

Summary

Red Hat Security Advisory: python38:3.8 and python38-devel:3.8 security update

Severity

Moderate

Scope

11 vulnerabilities in this advisory, including CVE-2021-29921.

CVE-2021-29921

9.1 (Critical)


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

Fixed: 239 products

https://access.redhat.com/errata/RHSA-2021:4162

Open the full advisory

SUSE-SU-2021:2940-1

Vulnerability from csaf_suse - Published: 2021-09-03 07:22 - Updated: 2021-09-03 07:22

Summary

Security update for python39

Severity

Important

Scope

1 vulnerability in this advisory, including CVE-2021-29921.

CVE-2021-29921

8.6 (High)


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

Recommended: 36 products

Open the full advisory

UBUNTU-CVE-2021-29921 (CVE-2021-29921)

Vulnerability from osv_ubuntu – Published: 2021-05-06 13:15 – Updated: 2026-04-22 07:40 – Source website

Details

Severity

9.8 (Critical)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2021-29921	REPORT
	https://github.com/python/cpython/pull/25099	REPORT
	https://sick.codes/sick-2021-014	REPORT
	https://python-security.readthedocs.io/vuln/ipadd…	REPORT
	https://github.com/sickcodes	REPORT
	https://github.com/sickcodes/security/blob/master…	REPORT
	https://github.com/python/cpython/pull/12577	REPORT
	https://docs.python.org/3/library/ipaddress.html	REPORT
	https://github.com/python/cpython/blob/63298930fb…	REPORT
	https://ubuntu.com/security/notices/USN-4973-1	ADVISORY
	https://ubuntu.com/security/notices/USN-4973-2	ADVISORY
	https://www.cve.org/CVERecord?id=CVE-2021-29921	REPORT
	https://ubuntu.com/security/notices/USN-6891-1	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "idle-python3.8",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "libpython3.8",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "libpython3.8-minimal",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "libpython3.8-stdlib",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "libpython3.8-testsuite",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "python3.8",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "python3.8-examples",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "python3.8-minimal",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          },
          {
            "binary_name": "python3.8-venv",
            "binary_version": "3.8.0-3ubuntu1~18.04.2+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "python3.8",
        "purl": "pkg:deb/ubuntu/python3.8@3.8.0-3ubuntu1~18.04.2+esm2?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.8.0-3ubuntu1~18.04.2+esm2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.8.0-3~18.04",
        "3.8.0-3~18.04.1",
        "3.8.0-3ubuntu1~18.04.2",
        "3.8.0-3ubuntu1~18.04.2+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "idle-python3.8",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "libpython3.8",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "libpython3.8-minimal",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "libpython3.8-stdlib",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "libpython3.8-testsuite",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "python3.8",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "python3.8-examples",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "python3.8-full",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "python3.8-minimal",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          },
          {
            "binary_name": "python3.8-venv",
            "binary_version": "3.8.10-0ubuntu1~20.04.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "python3.8",
        "purl": "pkg:deb/ubuntu/python3.8@3.8.10-0ubuntu1~20.04.1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.8.10-0ubuntu1~20.04.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.8.0-1",
        "3.8.0-2",
        "3.8.0-3",
        "3.8.0-4",
        "3.8.0-5",
        "3.8.1-2ubuntu3",
        "3.8.2~rc1-1ubuntu1",
        "3.8.2-1",
        "3.8.2-1ubuntu1",
        "3.8.2-1ubuntu1.1",
        "3.8.2-1ubuntu1.2",
        "3.8.5-1~20.04",
        "3.8.5-1~20.04.2",
        "3.8.5-1~20.04.3",
        "3.8.10-0ubuntu1~20.04"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "idle-python3.9",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "libpython3.9",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "libpython3.9-minimal",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "libpython3.9-stdlib",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "libpython3.9-testsuite",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "python3.9",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "python3.9-examples",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "python3.9-full",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "python3.9-minimal",
            "binary_version": "3.9.5-3~20.04.1"
          },
          {
            "binary_name": "python3.9-venv",
            "binary_version": "3.9.5-3~20.04.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "python3.9",
        "purl": "pkg:deb/ubuntu/python3.9@3.9.5-3~20.04.1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.9.5-3~20.04.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.9.0~rc1-1~20.04",
        "3.9.0-5~20.04"
      ]
    }
  ],
  "aliases": [],
  "details": "In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string. This (in some situations) allows attackers to bypass access control that is based on IP addresses.",
  "id": "UBUNTU-CVE-2021-29921",
  "modified": "2026-04-22T07:40:00Z",
  "published": "2021-05-06T13:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-29921"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/python/cpython/pull/25099"
    },
    {
      "type": "REPORT",
      "url": "https://sick.codes/sick-2021-014"
    },
    {
      "type": "REPORT",
      "url": "https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zeros.html"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/sickcodes"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-014.md"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/python/cpython/pull/12577"
    },
    {
      "type": "REPORT",
      "url": "https://docs.python.org/3/library/ipaddress.html"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915dbf1e17e9e1/Misc/NEWS.d/3.8.0a4.rst"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-4973-1"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-4973-2"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2021-29921"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-6891-1"
    }
  ],
  "related": [
    "USN-4973-1",
    "USN-4973-2",
    "USN-6891-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2021-29921"
  ]
}

WID-SEC-W-2022-0464

Vulnerability from csaf_certbund - Published: 2021-07-20 22:00 - Updated: 2025-04-29 22:00

Summary

Oracle Java SE: Mehrere Schwachstellen

Severity

Hoch

Scope

6 vulnerabilities in this advisory, including CVE-2021-29921.

CVE-2021-29921

Known affected: 31 products

Open the full advisory

WID-SEC-W-2023-2460

Vulnerability from csaf_certbund - Published: 2021-05-03 22:00 - Updated: 2024-12-01 23:00

Summary

Python: Schwachstelle ermöglicht Manipulation

Severity

Mittel

Scope

1 vulnerability in this advisory, including CVE-2021-29921.

CVE-2021-29921

Es existiert eine Schwachstelle in Python. Der Fehler besteht aufgrund einer unsachgemäßen Eingabevalidierung von oktalen Zeichenfolgen in der "stdlib ipaddress", was zu einer Server-Side Request Forgery führt. Ein entfernter anonymer Angreifer kann diese Schwachstelle ausnutzen, um Dateien zu manipulieren.

Known affected: 6 products Last affected: 1 product

Open the full advisory

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.

Detection rules are retrieved from Rulezet.

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

CVE-2021-29921 (GCVE-0-2021-29921)

RHSA-2021:3254

RHSA-2021:4160

RHSA-2021:4162

SUSE-SU-2021:2940-1

UBUNTU-CVE-2021-29921 (CVE-2021-29921)

WID-SEC-W-2022-0464

WID-SEC-W-2023-2460

Tags

Sightings

Nomenclature

Related by attack behaviour