# CVE-2026-50046: Possible heap use-after-free in an error path when a DoT forwarded query is jostled out CVE-2026-50046 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-50046, released July 28, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-50046 - Priority: Routine - CVSS: 5.9 (Moderate) - EPSS: 0.0024 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Jul 22, 2026 - Weakness: Use After Free - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50046 ## Description In NLnet Labs Unbound 1.15.0 up to and including 1.25.1, the TLS server name used for DNS-over-TLS (DoT) forwarded queries is tied to a struct's ('serviced_query') lifetime but also referenced by another struct ('waiting_tcp'). When the owning struct is jostled out of the mesh while the DoT TCP stream is still handshaking it frees the storage behind the referenced string and if the TLS stream then errors out, it dereferences the freed pointer. The dereference is read-only and the practical impact is a daemon crash resulting in denial of service. A malicious actor that knows a DoT forwarding/stub Unbound's configuration could exploit the vulnerability by quering records in the appropriate zone while keeping Unbound uder pressure so that the jostle logic kicks in. If answers for the vulnerable zone are slow, the likelihood of jostling such queries is higher, although the timing of the jostle needs to be precise. Requirements for a vulnerable Unbound is the existence of a stub/forward zone configured for DoT together with a configured '#authname' suffix on the server identification. The connectivity to the server needs to exhibit a transient failure at the correct time in order to kick off the vulnerable error path. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | python3-unbound amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | python3-unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound Debian 13.5 (trixie) | 1.26.1-0+deb13u1 | [DEBIAN-CVE-2026-50046](https://patchblox.com/security/data/fix/linux/debian-cve-2026-50046.md) | Jul 28, 2026 | | Linux | unbound Debian 14 | 1.25.2-1 | [DEBIAN-CVE-2026-50046](https://patchblox.com/security/data/fix/linux/debian-cve-2026-50046.md) | Jul 28, 2026 | | Linux | unbound amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound opensuse-leap 16.0 | 1.25.2-160000.1.1 | [OPENSUSE-SU-2026:21550-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21550-1.md) | Aug 10, 2026 | | Linux | unbound sles 15.6 | 1.25.2-150600.23.19.1 | [SUSE-SU-2026:3885-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3885-1.md) | Aug 31, 2026 | | Linux | unbound sles 15.7 | 1.25.2-150600.23.19.1 | [SUSE-SU-2026:3885-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3885-1.md) | Aug 31, 2026 | | Linux | unbound sles 16.0 | 1.25.2-160000.1.1 | [SUSE-SU-2026:23226-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23226-1.md) | Aug 10, 2026 | | Linux | unbound-anchor amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-anchor-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-debugsource amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-devel amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-libs amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-libs-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-utils amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | | Linux | unbound-utils-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.13 | [ALAS2023-2026-2033](https://patchblox.com/security/data/fix/linux/alas2023-2026-2033.md) | Aug 3, 2026 | --- Data as of 2026-11-08T19:12:23Z UTC. 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