GO-2026-4950

    Dashboard / Vulnerabilities / GO-2026-4950

    GO-2026-4950

    Published: 18 Aug 2026Last Modified: 19 Aug 2026

    Summary: Authorization bypass via double-encoded paths in github.com/valyala/fasthttp

    Details: In github.com/valyala/fasthttp before 1.70.0, ServeFile and ServeFS reinterpret filesystem paths as URIs, decoding percent-encoded sequences and treating characters like '?' and '#' as URI delimiters. In applications where authorization guards inspect ctx.Path() before passing paths to file-serving handlers, double-encoded path variants (e.g., /%2561dmin/export.csv) bypass access controls while still resolving to the protected file on disk.

    References: https://github.com/golang/vulndb/issues/4950, https://github.com/valyala/fasthttp/pull/2163, https://gist.github.com/thesmartshadow/af53acdfe0d6ce352d14eb86cecf5a08, https://github.com/valyala/fasthttp/releases/tag/v1.70.0

    Affected packages

    Package

    Name: github.com/valyala/fasthttp

    Purl: pkg:golang/github.com/valyala/fasthttp

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 0
    Fixed -1.70.0

    Affected versions

    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