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CVE-2026-40394

CVE-2026-40394

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

Varnish Cache 9 before 9.0.1 and Varnish Enterprise before 6.0.16r11 allows a "workspace overflow" denial of service (daemon panic) for certain amounts of prefetched data. The setup of an HTTP/2 session starts with a speculative HTTP/1 transport, and upon upgrading to h2 the HTTP/1 request is repurposed as stream zero. During the upgrade, a buffer allocation is made to reserve space to send frames to the client. This allocation would split the original workspace, and depending on the amount of prefetched data, the next fetch could perform a pipelining operation that would run out of workspace.

CVSS 4.0 · Medium · EPSS 0.2% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • varnish cache

    Versions
    • ≥ 9.0.0, < 9.0.1: Affected (semver)

    Update to 9.0.1

  • varnish Ubuntu:14.04:LTS

    Versions
    • 3.0.4-1ubuntu1
    • 3.0.4-1ubuntu2
    • 3.0.5-1ubuntu2
    • 3.0.5-2
    • 3.0.5-2ubuntu0.1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:Pro:16.04:LTS

    Versions
    • 4.0.3-1
    • 4.1.0-1
    • 4.1.0-2
    • 4.1.1-1
    • 4.1.1-1ubuntu0.2
    • 4.1.1-1ubuntu0.2+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:Pro:18.04:LTS

    Versions
    • 5.0.0-7.1
    • 5.2.1-1
    • 5.2.1-1ubuntu0.1
    • 5.2.1-1ubuntu0.1+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:Pro:20.04:LTS

    Versions
    • 6.1.1-1
    • 6.2.1-2
    • 6.2.1-2ubuntu0.1~esm1
    • 6.2.1-2ubuntu0.1~esm2
    • 6.2.1-2ubuntu0.1
    • 6.2.1-2ubuntu0.2
    • 6.2.1-2ubuntu0.2+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:Pro:22.04:LTS

    Versions
    • 6.5.2-1
    • 6.6.1-1
    • 6.6.1-1ubuntu0.2
    • 6.6.1-1ubuntu0.2+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:24.04:LTS

    Versions
    • 7.1.1-1.1ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:25.10

    Versions
    • 7.7.0-1
    • 7.7.0-2
    • 7.7.0-3
    • 7.7.3-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:26.10

    Versions
    • 7.7.3-1build1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • varnish Ubuntu:26.04:LTS

    Versions
    • 7.7.3-1
    • 7.7.3-1build1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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