CVE-2026-82720

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.

CVSS v3 5.9 MEDIUM

5.9^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt	Patch Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

History

23 Sep 2026, 19:49

Type	Values Removed	Values Added
CPE		cpe:2.3:a:nlnetlabs:unbound::::::::
First Time		Nlnetlabs Nlnetlabs unbound
References	~~() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt -~~	() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-82720.txt - Patch, Vendor Advisory

Information

Published : 2026-09-16 09:17

Updated : 2026-09-23 19:49

NVD link : CVE-2026-82720

Mitre link : CVE-2026-82720

CVE.ORG link : CVE-2026-82720

JSON object : View

Products Affected

nlnetlabs

unbound

CWE

CWE-416

Use After Free

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