CVE-2021-33503

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    CVE-2021-33503

    Published: 29 Jun 2021Last Modified: 7 Aug 2026

    Summary:

    Details: 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.

    References: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6SCV7ZNAHS3E6PBFLJGENCDRDRWRZZ6W/, https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FMUGWEAUYGGHTPPXT6YBD53WYXQGVV73/, https://github.com/advisories/GHSA-q2q7-5pp4-w6pg, https://security.gentoo.org/glsa/202107-36, https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec, https://www.oracle.com/security-alerts/cpuoct2021.html

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 7e856c04723036934fe314c63701466e4f42d2ee
    Fixed -d1616473df94b94f0f5ad19d2a6608cfe93b7cdf

    Affected versions

    1.26.4
    1.26.3
    1.26.2
    1.26.1
    1.26.0

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2021-33503 | CVE-DB