REDHAT-BUG-2479808: Use After Free
Use After Free vulnerability in the DNSSEC validator of the Unbound DNS resolver. The flaw is caused by a struct-assignment bug during deep-copying of response messages when DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1). The deep-copy operation overwrites the destination's rrsets pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. An adversary can exploit this vulnerability by controlling a malicious DNSSEC-signed zone and querying a vulnerable Unbound instance.
Affected Software
Event History
Frequently Asked Questions
What must an attacker be able to do to exploit this issue?
The attacker must control a malicious DNSSEC-signed zone and cause a vulnerable Unbound instance to query it. Exploitation depends on validation being suspended for a DS sub-query because the NSEC3 computational budget is exhausted.
Where can administrators find Red Hat remediation information?
Red Hat has published remediation information in RHSA-2026:23231 and RHSA-2026:24369, with additional tracking in Red Hat Bugzilla issue 2479808.