GO-2026-5026

    Dashboard / Vulnerabilities / GO-2026-5026

    GO-2026-5026

    Published: 22 May 2026Last Modified: 11 Sept 2026

    Summary: Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna

    Details: The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject "example.com" but permit "xn--example-.com". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name "example.com".

    References: https://go.dev/cl/767220, https://go.dev/issue/78760, https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8, https://groups.google.com/g/golang-announce/c/94pEornpRlI

    Affected packages

    Package

    Name: stdlib

    Purl: pkg:golang/stdlib

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 0
    Fixed -1.25.13

    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