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ALPINE-CVE-2026-55717

ALPINE-CVE-2026-55717

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

In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: <net> redirect' /'response-ip-data: <net> CNAME <target>' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash.

CVSS 5.9 · Medium · Fix available

Published
Updated

Stack: system

Affected products and versions

  • unbound Alpine:v3.22

    Affected ranges
    • ECOSYSTEM: ≥ 1.10.0, < 1.25.2-r0

    Update to 1.25.2-r0

  • unbound Alpine:v3.23

    Affected ranges
    • ECOSYSTEM: ≥ 1.10.0, < 1.25.2-r0

    Update to 1.25.2-r0

  • unbound Alpine:v3.24

    Affected ranges
    • ECOSYSTEM: ≥ 1.10.0, < 1.25.2-r0

    Update to 1.25.2-r0

Original sources

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