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CVE-2026-44453

CVE-2026-44453 · h2o is vulnerable to musl libc stack overflow

This page contains facts from public vulnerability sources. Check the original advisory before updating.

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 6b5370d, h2o is vulnerable to a Denial of Service attack when calling alloca under certain conditions. When serving static files, h2o builds the file path on stack, by calling alloca. The maximum size of the memory allocated using alloca can be as huge as ~600KB, which exceeds the default pthread stack size used by musl libc (128KB). If the amount of memory allocated by alloca exceeds the stack size, the h2o server crashes with a segmentation fault, while it tries to touch the guard page. This issue has been fixed by commit 6b5370d.

CVSS 7.5 · High · EPSS 0.5%

Published
Updated

Stack: system

Affected products and versions

  • h2o

    Versions
    • < 6b5370d: Affected

    No fix published

  • h2o Debian:12

    Versions
    • 2.2.5+dfsg2-10
    • 2.2.5+dfsg2-11
    • 2.2.5+dfsg2-7
    • 2.2.5+dfsg2-8
    • 2.2.5+dfsg2-8.1
    • 2.2.5+dfsg2-8.1~exp1
    • 2.2.5+dfsg2-9
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • h2o Ubuntu:Pro:18.04:LTS

    Versions
    • 2.2.3+dfsg-2
    • 2.2.4+dfsg-1
    • 2.2.4+dfsg-1build1
    • 2.2.4+dfsg-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • h2o Ubuntu:Pro:20.04:LTS

    Versions
    • 2.2.5+dfsg2-3
    • 2.2.5+dfsg2-3build1
    • 2.2.5+dfsg2-3ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • h2o Ubuntu:Pro:22.04:LTS

    Versions
    • 2.2.5+dfsg2-6
    • 2.2.5+dfsg2-6.1
    • 2.2.5+dfsg2-6.1ubuntu1
    • 2.2.5+dfsg2-6.1ubuntu2
    • 2.2.5+dfsg2-6.1ubuntu2+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • h2o Ubuntu:24.04:LTS

    Versions
    • 2.2.5+dfsg2-7
    • 2.2.5+dfsg2-8
    • 2.2.5+dfsg2-8.1ubuntu1
    • 2.2.5+dfsg2-8.1ubuntu2
    • 2.2.5+dfsg2-8.1ubuntu3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • dnsdist Ubuntu:Pro:24.04:LTS

    Versions
    • 1.8.0-1
    • 1.8.2-1
    • 1.8.2-2
    • 1.8.2-3
    • 1.8.3-1
    • 1.8.3-2
    • 1.8.3-2build1
    • 1.8.3-2build2
    • 1.8.3-2ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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