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.
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
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| 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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