UBUNTU-CVE-2026-91920

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    UBUNTU-CVE-2026-91920

    Published: 30 Oct 2026Last Modified: 5 Nov 2026
    Upstream:
    CVE-2026-91920

    Summary:

    Details: A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a specifically crafted 15-digit chunk size to bypass the limit and overflow into internal state flags. This can cause the server to terminate a request body prematurely and interpret the remaining data as a separate, smuggled request.

    References: https://ubuntu.com/security/CVE-2026-91920, https://www.cve.org/CVERecord?id=CVE-2026-91920, https://access.redhat.com/security/cve/CVE-2026-91920, https://bugzilla.redhat.com/show_bug.cgi?id=2528758

    Affected packages

    Package

    Name: undertow

    Purl: pkg:deb/ubuntu/undertow?arch=source&distro=esm-apps%2Fxenial

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -None

    Affected versions

    1.3.4-1
    1.3.5-1
    1.3.7-1
    1.3.11-1
    1.3.16-1
    1.3.16-1ubuntu0.1~esm1

    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
    UBUNTU-CVE-2026-91920 | CVE-DB