# CVE-2026-82720: Use-after-free in DoH stream cleanup code path CVE-2026-82720 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-82720, released September 19, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-82720 - Priority: Routine - CVSS: 5.9 (Moderate) - EPSS: 0.0038 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Sep 16, 2026 - Weakness: Use After Free - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-82720 ## Description NLnet Labs Unbound 1.12.0 up to and including 1.26.0 has a use-after-free vulnerability when compiled for DNS-over-HTTPs support with '--with-libnghttp2'. During failure code paths (i.e., RPZ drop query, jostle due to heavy traffic), a dropped DoH stream brings down the whole DoH session and does not account properly for other DoH streams in the same session. This leads to use-after-free in those code paths. If the prerequisites are satisfied (possible RPZ drop or heavy client traffic), a malicious actor can trigger the vulnerability with a single DoH connection and the appropriate traffic. Impact is limited as the reads are not user controlled and the use-after-free leads to early returns. However, a hardened allocator can catch the use-after-free and controllably terminate the process resulting to denial of service. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | python3-unbound amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | python3-unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound Debian 13.5 (trixie) | 1.26.1-0+deb13u1 | [DEBIAN-CVE-2026-82720](https://patchblox.com/security/data/fix/linux/debian-cve-2026-82720.md) | Sep 19, 2026 | | Linux | unbound Debian 14 | 1.26.1-1 | [DEBIAN-CVE-2026-82720](https://patchblox.com/security/data/fix/linux/debian-cve-2026-82720.md) | Sep 19, 2026 | | Linux | unbound amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound opensuse-leap 16.0 | 1.26.1-160000.1.1 | [OPENSUSE-SU-2026:22082-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22082-1.md) | Nov 7, 2026 | | Linux | unbound sles 15.6 | 1.26.1-150600.23.24.1 | [SUSE-SU-2026:4620-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4620-1.md) | Nov 7, 2026 | | Linux | unbound sles 15.7 | 1.26.1-150600.23.24.1 | [SUSE-SU-2026:4620-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4620-1.md) | Nov 7, 2026 | | Linux | unbound sles 16.0 | 1.26.1-160000.1.1 | [SUSE-SU-2026:24226-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24226-1.md) | Nov 7, 2026 | | Linux | unbound-anchor amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-anchor-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-debugsource amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-devel amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-libs amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-libs-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-utils amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | | Linux | unbound-utils-debuginfo amzn 2023 | 1.17.1-1.amzn2023.0.15 | [ALAS2023-2026-3127](https://patchblox.com/security/data/fix/linux/alas2023-2026-3127.md) | Sep 28, 2026 | --- Data as of 2026-11-09T19:38:12Z UTC. 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