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.
History

Wed, 23 Sep 2026 20:00:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

Thu, 17 Sep 2026 21:00:00 +0000

Type Values Removed Values Added
First Time appeared Nlnetlabs
Nlnetlabs unbound
Vendors & Products Nlnetlabs
Nlnetlabs unbound

Wed, 16 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 16 Sep 2026 12:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-825
References
Metrics threat_severity

None

threat_severity

Moderate


Wed, 16 Sep 2026 08:45:00 +0000

Type Values Removed Values Added
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.
Title Use-after-free in DoH stream cleanup code path
Weaknesses CWE-416
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: NLnet Labs

Published: 2026-09-16T08:32:10.359Z

Updated: 2026-09-16T14:14:25.720Z

Reserved: 2026-09-07T14:06:21.960Z

Link: CVE-2026-82720

cve-icon Vulnrichment

Updated: 2026-09-16T14:13:12.445Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-16T09:17:06.677

Modified: 2026-09-23T19:49:08.910

Link: CVE-2026-82720

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-16T08:32:10Z

Links: CVE-2026-82720 - Bugzilla