CVE-2026-81642 PUBLISHED

Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY

Assigner: NLnet Labs
Reserved: 07.09.2026 Published: 16.09.2026 Updated: 16.09.2026

In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a malicious zone and querying a vulnerable Unbound.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red
CVSS Score: 9.1

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	High
Attack Complexity	Low	Integrity	High	Integrity	High
Attack Requirements	None	Availability	High	Availability	High
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	NLnet Labs
Product	Unbound
Versions	Default: unaffected affected from 0 to 1.26.1 (excl.)

Solutions

This issue is fixed starting with version 1.26.1

Credits

Yuqi Qiu (Nankai University, AOSP Lab) finder
Xiang Li (Nankai University, AOSP Lab) finder

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81642.txt

Problem Types

CWE-122: Heap-based Buffer Overflow CWE