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CVE-2026-5947

CVE-2026-5947 · SIG(0) validation during query flood may lead to undefined behavior

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

Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.

CVSS 7.5 · High · EPSS 0.8% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • bind 9

    Versions
    • ≥ 9.20.0, ≤ 9.20.22: Affected (custom)
    • ≥ 9.21.0, ≤ 9.21.21: Affected (custom)
    • ≥ 9.20.9-S1, ≤ 9.20.22-S1: Affected (custom)
    • ≥ 9.18.28, ≤ 9.18.49: Not affected (custom)
    • ≥ 9.18.28-S1, ≤ 9.18.49-S1: Not affected (custom)

    No fix published

  • bind9 Debian:13

    Versions
    • 1:9.20.11-4
    • 1:9.20.15-1
    • 1:9.20.15-1~deb13u1
    • 1:9.20.15-1~deb13u1~bpo12+1
    • 1:9.20.15-2
    • 1:9.20.18-1
    • 1:9.20.18-1~deb13u1
    • 1:9.20.18-1~deb13u1~bpo12+1
    • 1:9.20.19-1
    • 1:9.20.19-1~bpo12+1
    • 1:9.20.20-1
    • 1:9.20.20-1~bpo12+1
    • 1:9.20.21-1
    • 1:9.20.21-1~deb13u1
    • 1:9.20.21-1~deb13u1~bpo12+1
    • 1:9.20.22-1
    • 1:9.20.23-1~deb13u1~bpo12+1
    Affected ranges
    • ECOSYSTEM: < 1:9.20.23-1~deb13u1

    Update to 1:9.20.23-1~deb13u1

  • bind9 Debian:14

    Versions
    • 1:9.20.11-4
    • 1:9.20.15-1
    • 1:9.20.15-1~deb13u1
    • 1:9.20.15-1~deb13u1~bpo12+1
    • 1:9.20.15-2
    • 1:9.20.18-1
    • 1:9.20.18-1~deb13u1
    • 1:9.20.18-1~deb13u1~bpo12+1
    • 1:9.20.19-1
    • 1:9.20.19-1~bpo12+1
    • 1:9.20.20-1
    • 1:9.20.20-1~bpo12+1
    • 1:9.20.21-1
    • 1:9.20.21-1~deb13u1
    • 1:9.20.21-1~deb13u1~bpo12+1
    • 1:9.20.22-1
    • 1:9.20.23-1~deb13u1
    • 1:9.20.23-1~deb13u1~bpo12+1
    Affected ranges
    • ECOSYSTEM: < 1:9.20.23-1

    Update to 1:9.20.23-1

  • bind9 Ubuntu:25.10

    Versions
    • 1:9.20.4-3ubuntu1
    • 1:9.20.4-3ubuntu2
    • 1:9.20.4-3ubuntu3
    • 1:9.20.9-2ubuntu1
    • 1:9.20.10-1ubuntu1
    • 1:9.20.11-1ubuntu1
    • 1:9.20.11-1ubuntu2
    • 1:9.20.11-1ubuntu2.1
    • 1:9.20.11-1ubuntu2.2
    Affected ranges
    • ECOSYSTEM: < 1:9.20.11-1ubuntu2.4

    Update to 1:9.20.11-1ubuntu2.4

  • bind9 Ubuntu:26.04:LTS

    Versions
    • 1:9.20.11-1ubuntu2
    • 1:9.20.11-1ubuntu3
    • 1:9.20.18-1ubuntu1
    • 1:9.20.18-1ubuntu2
    Affected ranges
    • ECOSYSTEM: < 1:9.20.18-1ubuntu2.1

    Update to 1:9.20.18-1ubuntu2.1

Original sources

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