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CVE-2026-5950

CVE-2026-5950 · Unbounded resend loop in BIND 9 resolver

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

An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

CVSS 5.3 · Medium · EPSS 0.8% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • bind 9

    Versions
    • ≥ 9.18.36, ≤ 9.18.48: Affected (custom)
    • ≥ 9.20.8, ≤ 9.20.22: Affected (custom)
    • ≥ 9.21.7, ≤ 9.21.21: Affected (custom)
    • ≥ 9.18.36-S1, ≤ 9.18.48-S1: Affected (custom)
    • ≥ 9.20.9-S1, ≤ 9.20.22-S1: Affected (custom)

    No fix published

  • bind9 Debian:12

    Versions
    • 1:9.18.12-1
    • 1:9.18.13-1
    • 1:9.18.16-1
    • 1:9.18.16-1~deb12u1
    • 1:9.18.16-1~deb12u1~bpo11+1
    • 1:9.18.19-1~deb12u1
    • 1:9.18.19-1~deb12u1~bpo11+1
    • 1:9.18.24-1
    • 1:9.18.24-1~bpo11+1
    • 1:9.18.28-1~deb12u1
    • 1:9.18.28-1~deb12u2
    • 1:9.18.33-1~deb12u2
    • 1:9.18.41-1~deb12u1
    • 1:9.18.44-1~deb12u1
    • 1:9.18.47-1~deb12u1
    • 1:9.18.49-1~deb12u1
    Affected ranges
    • ECOSYSTEM: < 1:9.18.49-1~deb12u2

    Update to 1:9.18.49-1~deb12u2

  • 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

  • isc-dhcp Ubuntu:18.04:LTS

    Versions
    • 4.3.5-3ubuntu2
    • 4.3.5-3ubuntu3
    • 4.3.5-3ubuntu4
    • 4.3.5-3ubuntu5
    • 4.3.5-3ubuntu6
    • 4.3.5-3ubuntu7
    • 4.3.5-3ubuntu7.1
    • 4.3.5-3ubuntu7.2
    • 4.3.5-3ubuntu7.3
    • 4.3.5-3ubuntu7.4
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • bind9-libs Ubuntu:20.04:LTS

    Versions
    • 1:9.11.16+dfsg-3~build1
    • 1:9.11.16+dfsg-3~ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • bind9 Ubuntu:22.04:LTS

    Versions
    • 1:9.16.15-1ubuntu1
    • 1:9.16.15-1ubuntu2
    • 1:9.16.15-1ubuntu3
    • 1:9.18.0-2ubuntu1
    • 1:9.18.0-2ubuntu2
    • 1:9.18.0-2ubuntu3
    • 1:9.18.1-1ubuntu1
    • 1:9.18.1-1ubuntu1.1
    • 1:9.18.1-1ubuntu1.2
    • 1:9.18.1-1ubuntu1.3
    • 1:9.18.12-0ubuntu0.22.04.1
    • 1:9.18.12-0ubuntu0.22.04.2
    • 1:9.18.12-0ubuntu0.22.04.3
    • 1:9.18.18-0ubuntu0.22.04.1
    • 1:9.18.18-0ubuntu0.22.04.2
    • 1:9.18.24-0ubuntu0.22.04.1
    • 1:9.18.28-0ubuntu0.22.04.1
    • 1:9.18.30-0ubuntu0.22.04.1
    • 1:9.18.30-0ubuntu0.22.04.2
    • 1:9.18.39-0ubuntu0.22.04.1
    • 1:9.18.39-0ubuntu0.22.04.2
    • 1:9.18.39-0ubuntu0.22.04.3
    Affected ranges
    • ECOSYSTEM: < 1:9.18.39-0ubuntu0.22.04.4

    Update to 1:9.18.39-0ubuntu0.22.04.4

  • bind9-libs Ubuntu:22.04:LTS

    Versions
    • 1:9.11.19+dfsg-2.1ubuntu1
    • 1:9.11.19+dfsg-2.1ubuntu2
    • 1:9.11.19+dfsg-2.1ubuntu3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • bind9 Ubuntu:24.04:LTS

    Versions
    • 1:9.18.18-0ubuntu2
    • 1:9.18.21-0ubuntu1
    • 1:9.18.24-0ubuntu3
    • 1:9.18.24-0ubuntu4
    • 1:9.18.24-0ubuntu5
    • 1:9.18.28-0ubuntu0.24.04.1
    • 1:9.18.30-0ubuntu0.24.04.1
    • 1:9.18.30-0ubuntu0.24.04.2
    • 1:9.18.39-0ubuntu0.24.04.1
    • 1:9.18.39-0ubuntu0.24.04.2
    • 1:9.18.39-0ubuntu0.24.04.3
    Affected ranges
    • ECOSYSTEM: < 1:9.18.39-0ubuntu0.24.04.5

    Update to 1:9.18.39-0ubuntu0.24.04.5

  • isc-dhcp Ubuntu:24.04:LTS

    Versions
    • 4.4.3-P1-2ubuntu5
    • 4.4.3-P1-4ubuntu1
    • 4.4.3-P1-4ubuntu2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • 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

  • isc-dhcp Ubuntu:25.10

    Versions
    • 4.4.3-P1-4ubuntu2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • 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

  • isc-dhcp Ubuntu:26.04:LTS

    Versions
    • 4.4.3-P1-4ubuntu2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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