Description
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.
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Remediation
Vendor Solution
This issue is fixed starting with version 1.25.2
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History
Wed, 22 Jul 2026 13:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | Libunbound applications configured with 'unwanted-reply-threshold' could eventually be abruptly terminated | |
| Weaknesses | CWE-754 | |
| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: NLnet Labs
Published:
Updated: 2026-07-22T14:21:22.388Z
Reserved: 2026-06-22T10:11:10.524Z
Link: CVE-2026-44621
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Weaknesses