CVE-2026-44621

Libunbound applications configured with 'unwanted-reply-threshold' could eventually be abruptly terminated

CVE-2026-44621 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-44621, released July 28, 2026. It is not reported as exploited. Patch Radar priority: Routine.

Routine
CVSS
5.9
Moderate
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0025
16th percentile

With NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with 'unwanted-reply-threshold', could eventually be abruptly terminated if the threshold is reached and libunbound needs to call 'libworker_alloc_cleanup' since the function is absent from the function call allow list. When an application using libunbound sets 'unwanted-reply-threshold' to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the 'libworker_alloc_cleanup' will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function 'worker_alloc_cleanup' is registed in the allow list and proceeds to perform the documented cache flush.

Where it's fixed

ProductFixed inFixReleased
Linux
python3-unbound · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
python3-unbound-debuginfo · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound · Debian 13.5 (trixie) 1.26.1-0+deb13u1 DEBIAN-CVE-2026-44621 Jul 28, 2026
unbound · Debian 14 1.25.2-1 DEBIAN-CVE-2026-44621 Jul 28, 2026
unbound · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound · opensuse-leap 16.0 1.25.2-160000.1.1 OPENSUSE-SU-2026:21550-1 Aug 10, 2026
unbound · sles 15.6 1.25.2-150600.23.19.1 SUSE-SU-2026:3885-1 Aug 31, 2026
unbound · sles 15.7 1.25.2-150600.23.19.1 SUSE-SU-2026:3885-1 Aug 31, 2026
unbound · sles 16.0 1.25.2-160000.1.1 SUSE-SU-2026:23226-1 Aug 10, 2026
unbound-anchor · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-anchor-debuginfo · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-debuginfo · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-debugsource · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-devel · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-libs · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-libs-debuginfo · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-utils · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026
unbound-utils-debuginfo · amzn 2023 1.17.1-1.amzn2023.0.13 ALAS2023-2026-2033 Aug 3, 2026

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