CVE-2026-81642: Heap buffer overflow and possible Remote Code Execution when digesting DNSKEY
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Unboundto a version that resolves this vulnerability.Fixed in 1.26.1
Event History
Frequently Asked Questions
Which deployments are realistically exposed?
Unbound deployments up to and including 1.26.0 are exposed when they can be induced to query a malicious zone. The vulnerable component is the DNSSEC validator.
What does an attacker need to exploit this issue?
An attacker needs control of a malicious DNS zone and must cause a vulnerable Unbound instance to query it. The malicious DNSKEY uses an owner compression pointer to its own RDATA.
What is the potential impact?
The issue can cause denial of service through a heap buffer overflow. Possible remote code execution is also described because the overflow can involve attacker-controlled data.