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CVE-2026-84961

CVE-2026-84961 · undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool

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

undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-supplied checkServerIdentity callback or a custom connector inside the connect option, is silently discarded before it reaches the TLS layer. As a result a peer whose certificate the application's custom checkServerIdentity was written to reject, but which still passes Node's default hostname and chain checks, is accepted when reached through BalancedPool. The Client, Pool, and Agent dispatchers are not affected because they extract the connect and tls options before cloning. This affects undici versions from 7.24.1 up to 7.29.1 and from 8.0.0 up to 8.10.2, and only when the application supplies a function-valued connect or tls option to BalancedPool. Users should upgrade to undici 7.29.1 or 8.10.2.

CVSS 7.4 · High · EPSS 0.2% · Fix available

Published
Updated

Stack: system · node

Affected products and versions

  • undici

    Versions
    • ≥ 7.24.1, < 7.29.1: Affected (semver)
    • 7.29.1: Not affected (semver)
    • ≥ 8.0.0, < 8.10.2: Affected (semver)
    • 8.10.2: Not affected (semver)

    Update to 7.29.1; Update to 8.10.2

  • node-undici Debian:12

    Versions
    • 5.15.0+dfsg1+~cs20.10.9.3-1
    • 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u1
    • 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u2
    • 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u3
    • 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u4
    • 5.19.1+dfsg1+~cs20.10.9.5-1
    • 5.19.1+dfsg1+~cs20.10.9.5-2
    • 5.22.1+dfsg1+~cs20.10.10.2-1
    • 5.26.3+dfsg1+~cs23.10.12-1
    • 5.26.3+dfsg1+~cs23.10.12-2
    • 5.26.3+dfsg1+~cs23.10.12-3
    • 5.28.0+dfsg1+~cs23.11.12.3-1
    • 5.28.0+dfsg1+~cs23.11.12.3-2
    • 5.28.2+dfsg1+~cs23.11.12.3-1
    • 5.28.2+dfsg1+~cs23.11.12.3-2
    • 5.28.2+dfsg1+~cs23.11.12.3-3
    • 5.28.2+dfsg1+~cs23.11.12.3-4
    • 5.28.2+dfsg1+~cs23.11.12.3-5
    • 5.28.2+dfsg1+~cs23.11.12.3-6
    • 5.28.4+dfsg1+~cs23.12.11-1
    • 5.28.4+dfsg1+~cs23.12.11-2
    • 7.1.0+dfsg1+~cs24.12.10-1
    • 7.15.0+dfsg+~cs3.2.0-1
    • 7.15.0+dfsg+~cs3.2.0-3
    • 7.16.0+dfsg+~cs3.2.0-1
    • 7.16.0+dfsg+~cs3.2.0-2
    • 7.18.2+dfsg+~cs3.2.0-1
    • 7.2.3+dfsg1+~cs24.12.11-1
    • 7.2.3+dfsg1+~cs24.12.11-2
    • 7.24.5+dfsg+~cs3.2.0-1
    • 7.24.6+dfsg+~cs3.2.0-1
    • 7.24.6+dfsg+~cs3.2.0-2
    • 7.24.6+dfsg+~cs3.2.0-3
    • 7.3.0+dfsg1+~cs24.12.11-1
    • 7.3.0+dfsg1+~cs24.12.11-2
    • 8.10.2+dfsg+~cs3.2.2-1
    • 8.5.0+dfsg+~cs3.2.0-1
    • 8.5.0+dfsg+~cs3.2.0-2
    • 8.5.0+dfsg+~cs3.2.0-3
    • 8.9.0+dfsg+~cs3.2.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-undici Debian:13

    Versions
    • 7.15.0+dfsg+~cs3.2.0-1
    • 7.15.0+dfsg+~cs3.2.0-3
    • 7.16.0+dfsg+~cs3.2.0-1
    • 7.16.0+dfsg+~cs3.2.0-2
    • 7.18.2+dfsg+~cs3.2.0-1
    • 7.24.5+dfsg+~cs3.2.0-1
    • 7.24.6+dfsg+~cs3.2.0-1
    • 7.24.6+dfsg+~cs3.2.0-2
    • 7.24.6+dfsg+~cs3.2.0-3
    • 7.3.0+dfsg1+~cs24.12.11-1
    • 7.3.0+dfsg1+~cs24.12.11-2
    • 8.10.2+dfsg+~cs3.2.2-1
    • 8.5.0+dfsg+~cs3.2.0-1
    • 8.5.0+dfsg+~cs3.2.0-2
    • 8.5.0+dfsg+~cs3.2.0-3
    • 8.9.0+dfsg+~cs3.2.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-undici Debian:14

    Versions
    • 7.15.0+dfsg+~cs3.2.0-1
    • 7.15.0+dfsg+~cs3.2.0-3
    • 7.16.0+dfsg+~cs3.2.0-1
    • 7.16.0+dfsg+~cs3.2.0-2
    • 7.18.2+dfsg+~cs3.2.0-1
    • 7.24.5+dfsg+~cs3.2.0-1
    • 7.24.6+dfsg+~cs3.2.0-1
    • 7.24.6+dfsg+~cs3.2.0-2
    • 7.24.6+dfsg+~cs3.2.0-3
    • 7.3.0+dfsg1+~cs24.12.11-1
    • 7.3.0+dfsg1+~cs24.12.11-2
    • 8.5.0+dfsg+~cs3.2.0-1
    • 8.5.0+dfsg+~cs3.2.0-2
    • 8.5.0+dfsg+~cs3.2.0-3
    • 8.9.0+dfsg+~cs3.2.0-1
    Affected ranges
    • ECOSYSTEM: < 8.10.2+dfsg+~cs3.2.2-1

    Update to 8.10.2+dfsg+~cs3.2.2-1

  • undici npm

    Affected ranges
    • SEMVER: ≥ 7.24.1, < 7.29.1

    Update to 7.29.1

  • undici npm

    Affected ranges
    • SEMVER: ≥ 8.0.0, < 8.10.2

    Update to 8.10.2

  • node-undici Ubuntu:24.04:LTS

    Versions
    • 5.22.1+dfsg1+~cs20.10.10.2-1ubuntu1
    • 5.26.3+dfsg1+~cs23.10.12-2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-undici Ubuntu:26.10

    Versions
    • 7.18.2+dfsg+~cs3.2.0-1build1
    • 7.24.6+dfsg+~cs3.2.0-3
    • 8.5.0+dfsg+~cs3.2.0-2
    • 8.5.0+dfsg+~cs3.2.0-3
    • 8.9.0+dfsg+~cs3.2.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-undici Ubuntu:26.04:LTS

    Versions
    • 7.3.0+dfsg1+~cs24.12.11-2
    • 7.16.0+dfsg+~cs3.2.0-2
    • 7.18.2+dfsg+~cs3.2.0-1
    • 7.18.2+dfsg+~cs3.2.0-1build1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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