GHSA-q2q7-5pp4-w6pg

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    GHSA-q2q7-5pp4-w6pg

    Published: 1 Jun 2021Last Modified: 8 Jul 2026

    Summary: Catastrophic backtracking in URL authority parser when passed URL containing many @ characters

    Details: ### Impact 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. ### Patches The issue has been fixed in urllib3 v1.26.5. ### References - [CVE-2021-33503](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-33503) - [JVNVU#92413403 (English)](https://jvn.jp/en/vu/JVNVU92413403/) - [JVNVU#92413403 (Japanese)](https://jvn.jp/vu/JVNVU92413403/) - [urllib3 v1.26.5](https://github.com/urllib3/urllib3/releases/tag/1.26.5) ### For more information If you have any questions or comments about this advisory: * Ask in our [community Discord](https://discord.gg/urllib3) * Email [[email protected]](mailto:[email protected])

    References: https://github.com/urllib3/urllib3/security/advisories/GHSA-q2q7-5pp4-w6pg, https://nvd.nist.gov/vuln/detail/CVE-2021-33503, https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec, https://github.com/urllib3/urllib3/commit/5b047b645f5f93900d5e2fc31230848c25eb1f5f#diff-52026d639119bf1e0364836b4e8a18bd9ed3c95c6ba39b26534a5057a65e35bbR65, https://github.com/advisories/GHSA-q2q7-5pp4-w6pg, https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2021-108.yaml, https://github.com/urllib3/urllib3, https://lists.fedoraproject.org/archives/list/[email protected]/message/6SCV7ZNAHS3E6PBFLJGENCDRDRWRZZ6W, https://lists.fedoraproject.org/archives/list/[email protected]/message/FMUGWEAUYGGHTPPXT6YBD53WYXQGVV73, https://security.gentoo.org/glsa/202107-36, https://www.oracle.com/security-alerts/cpuoct2021.html

    Affected packages

    Package

    Name: urllib3

    Purl: pkg:pypi/urllib3

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 1.25.4
    Fixed -1.26.5

    Affected versions

    1.25.10
    1.25.11
    1.25.4
    1.25.5
    1.25.6
    1.25.7
    1.25.8
    1.25.9

    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
    GHSA-q2q7-5pp4-w6pg | CVE-DB