NULL Pointer Dereference Affecting unbound-munin package, versions <0:1.25.2-0.1.hum1


Severity

Recommended
0.0
medium
0
10

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.24% (15th percentile)

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  • Snyk IDSNYK-RHEL10-UNBOUNDMUNIN-18979828
  • published20 Aug 2026
  • disclosed22 Jul 2026

Introduced: 22 Jul 2026

NewCVE-2026-55717  (opens in a new tab)
CWE-476  (opens in a new tab)

How to fix?

Upgrade RHEL:10 unbound-munin to version 0:1.25.2-0.1.hum1 or higher.
This issue was patched in RHSA-2026:43588.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound-munin package and not the unbound-munin package as distributed by RHEL. See How to fix? for RHEL:10 relevant fixed versions and status.

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 Base Scores

version 3.1