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CVE-2021-33503 (GCVE-0-2021-33503)

Vulnerability from cvelistv5 – Published: 2021-06-29 10:55 – Updated: 2024-08-03 23:50
VLAI
Summary
An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • n/a
Assigner
References
Show details on NVD website
To clipboard 

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                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 3.6,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ]
        },
        "published": "2021-06-29T11:15:07.847",
        "references": [
          {
            "source": "cve@mitre.org",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://github.com/advisories/GHSA-q2q7-5pp4-w6pg"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec"
          },
          {
            "source": "cve@mitre.org",
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6SCV7ZNAHS3E6PBFLJGENCDRDRWRZZ6W/"
          },
          {
            "source": "cve@mitre.org",
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FMUGWEAUYGGHTPPXT6YBD53WYXQGVV73/"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://security.gentoo.org/glsa/202107-36"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://www.oracle.com/security-alerts/cpuoct2021.html"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://github.com/advisories/GHSA-q2q7-5pp4-w6pg"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6SCV7ZNAHS3E6PBFLJGENCDRDRWRZZ6W/"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FMUGWEAUYGGHTPPXT6YBD53WYXQGVV73/"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://security.gentoo.org/glsa/202107-36"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://www.oracle.com/security-alerts/cpuoct2021.html"
          }
        ],
        "sourceIdentifier": "cve@mitre.org",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-400"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-28T06:11:38+00:00",
      "cve": "CVE-2021-33503",
      "id": "CVE-2021-33503",
      "initial_release_date": "2021-06-01T00:00:00+00:00",
      "product_status:fixed": "625",
      "product_status:known_affected": "4",
      "product_status:known_not_affected": "1509",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "python-urllib3: ReDoS in the parsing of authority part of URL",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-33503.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-03T00:48:06Z",
      "cve": "CVE-2021-33503",
      "id": "CVE-2021-33503",
      "initial_release_date": "2023-02-15T03:40:24Z",
      "product_status:known_affected": "332",
      "product_status:known_not_affected": "20",
      "product_status:recommended": "172",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-33503",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-33503.json",
      "version": "56"
    }
  }
}



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Tags
Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.


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.