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CVE-2026-42959

CVE-2026-42959 · Crash during DNSSEC validation of malicious content

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

NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets.

CVSS 8.7 · High · EPSS 0.8% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • unbound

    Versions
    • ≥ 0, < 1.25.1: Affected (semver)

    Update to 1.25.1

  • unbound Debian:12

    Versions
    • 1.17.1-2
    • 1.17.1-2+deb12u1
    • 1.17.1-2+deb12u2
    • 1.17.1-2+deb12u3
    • 1.17.1-2+deb12u4
    • 1.17.1-2+loong64
    • 1.18.0-1
    • 1.18.0-2
    • 1.19.1-1
    • 1.19.2-1
    • 1.20.0-1
    • 1.21.1-1
    • 1.22.0-1
    • 1.22.0-2
    • 1.23.1-1
    • 1.24.0-1
    • 1.24.0-2
    • 1.24.1-1
    • 1.24.1-2
    • 1.24.2-1
    • 1.25.0-1
    • 1.25.1-1
    • 1.25.2-1
    • 1.26.0-1
    • 1.26.0-2
    • 1.26.1-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • unbound Debian:13

    Versions
    • 1.22.0-2
    • 1.22.0-2+deb13u1
    • 1.22.0-2+deb13u2
    Affected ranges
    • ECOSYSTEM: < 1.22.0-2+deb13u3

    Update to 1.22.0-2+deb13u3

  • unbound Debian:14

    Versions
    • 1.22.0-2
    • 1.23.1-1
    • 1.24.0-1
    • 1.24.0-2
    • 1.24.1-1
    • 1.24.1-2
    • 1.24.2-1
    • 1.25.0-1
    Affected ranges
    • ECOSYSTEM: < 1.25.1-1

    Update to 1.25.1-1

  • unbound Ubuntu:Pro:14.04:LTS

    Versions
    • 1.4.20-1
    • 1.4.21-1
    • 1.4.21-1ubuntu1
    • 1.4.21-1ubuntu2
    • 1.4.22-1ubuntu1
    • 1.4.22-1ubuntu2
    • 1.4.22-1ubuntu3
    • 1.4.22-1ubuntu4
    • 1.4.22-1ubuntu4.14.04.1
    • 1.4.22-1ubuntu4.14.04.2
    • 1.4.22-1ubuntu4.14.04.3
    • 1.4.22-1ubuntu4.14.04.3+esm1
    • 1.4.22-1ubuntu4.14.04.3+esm2
    Affected ranges
    • ECOSYSTEM: < 1.4.22-1ubuntu4.14.04.3+esm3

    Update to 1.4.22-1ubuntu4.14.04.3+esm3

  • unbound Ubuntu:Pro:16.04:LTS

    Versions
    • 1.4.22-1ubuntu6
    • 1.5.7-1ubuntu1
    • 1.5.7-1ubuntu2
    • 1.5.8-1ubuntu1
    • 1.5.8-1ubuntu1.1
    • 1.5.8-1ubuntu1.1+esm1
    • 1.5.8-1ubuntu1.1+esm2
    Affected ranges
    • ECOSYSTEM: < 1.5.8-1ubuntu1.1+esm3

    Update to 1.5.8-1ubuntu1.1+esm3

  • unbound Ubuntu:Pro:18.04:LTS

    Versions
    • 1.6.5-1
    • 1.6.7-1
    • 1.6.7-1build1
    • 1.6.7-1ubuntu1
    • 1.6.7-1ubuntu2
    • 1.6.7-1ubuntu2.1
    • 1.6.7-1ubuntu2.2
    • 1.6.7-1ubuntu2.3
    • 1.6.7-1ubuntu2.4
    • 1.6.7-1ubuntu2.5
    • 1.6.7-1ubuntu2.6
    • 1.6.7-1ubuntu2.6+esm2
    • 1.6.7-1ubuntu2.6+esm3
    Affected ranges
    • ECOSYSTEM: < 1.6.7-1ubuntu2.6+esm4

    Update to 1.6.7-1ubuntu2.6+esm4

  • unbound Ubuntu:Pro:20.04:LTS

    Versions
    • 1.9.0-2ubuntu1
    • 1.9.0-2ubuntu2
    • 1.9.4-2
    • 1.9.4-2ubuntu1
    • 1.9.4-2ubuntu1.1
    • 1.9.4-2ubuntu1.2
    • 1.9.4-2ubuntu1.3
    • 1.9.4-2ubuntu1.4
    • 1.9.4-2ubuntu1.5
    • 1.9.4-2ubuntu1.6
    • 1.9.4-2ubuntu1.8
    • 1.9.4-2ubuntu1.9
    • 1.9.4-2ubuntu1.11
    Affected ranges
    • ECOSYSTEM: < 1.9.4-2ubuntu1.11+esm1

    Update to 1.9.4-2ubuntu1.11+esm1

  • unbound Ubuntu:22.04:LTS

    Versions
    • 1.13.1-1ubuntu1
    • 1.13.1-1ubuntu3
    • 1.13.1-1ubuntu5
    • 1.13.1-1ubuntu5.1
    • 1.13.1-1ubuntu5.2
    • 1.13.1-1ubuntu5.3
    • 1.13.1-1ubuntu5.4
    • 1.13.1-1ubuntu5.5
    • 1.13.1-1ubuntu5.7
    • 1.13.1-1ubuntu5.8
    • 1.13.1-1ubuntu5.10
    • 1.13.1-1ubuntu5.11
    • 1.13.1-1ubuntu5.12
    • 1.13.1-1ubuntu5.13
    • 1.13.1-1ubuntu5.14
    Affected ranges
    • ECOSYSTEM: < 1.13.1-1ubuntu5.15

    Update to 1.13.1-1ubuntu5.15

  • unbound Ubuntu:24.04:LTS

    Versions
    • 1.17.1-2
    • 1.18.0-2ubuntu1
    • 1.18.0-2ubuntu2
    • 1.19.1-1ubuntu1
    • 1.19.2-1ubuntu1
    • 1.19.2-1ubuntu3
    • 1.19.2-1ubuntu3.1
    • 1.19.2-1ubuntu3.2
    • 1.19.2-1ubuntu3.3
    • 1.19.2-1ubuntu3.4
    • 1.19.2-1ubuntu3.5
    • 1.19.2-1ubuntu3.6
    • 1.19.2-1ubuntu3.7
    Affected ranges
    • ECOSYSTEM: < 1.19.2-1ubuntu3.8

    Update to 1.19.2-1ubuntu3.8

  • unbound Ubuntu:25.10

    Versions
    • 1.22.0-1ubuntu1
    • 1.22.0-2ubuntu1
    • 1.22.0-2ubuntu2
    • 1.22.0-2ubuntu2.1
    • 1.22.0-2ubuntu2.2
    Affected ranges
    • ECOSYSTEM: < 1.22.0-2ubuntu2.3

    Update to 1.22.0-2ubuntu2.3

  • unbound Ubuntu:26.04:LTS

    Versions
    • 1.22.0-2ubuntu2
    • 1.22.0-2ubuntu4
    • 1.24.2-1ubuntu1
    • 1.24.2-1ubuntu2
    Affected ranges
    • ECOSYSTEM: < 1.24.2-1ubuntu2.1

    Update to 1.24.2-1ubuntu2.1

Original sources

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