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ALPINE-CVE-2026-42959

ALPINE-CVE-2026-42959

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 7.5 · High · Fix available

Published
Updated

Stack: system

Affected products and versions

  • unbound Alpine:v3.22

    Affected ranges
    • ECOSYSTEM: < 1.25.2-r0

    Update to 1.25.2-r0

  • unbound Alpine:v3.23

    Affected ranges
    • ECOSYSTEM: < 1.25.2-r0

    Update to 1.25.2-r0

  • unbound Alpine:v3.24

    Affected ranges
    • ECOSYSTEM: < 1.25.1-r0

    Update to 1.25.1-r0

Original sources

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