Bug 2479808 (CVE-2026-33278) - CVE-2026-33278 unbound: Unbound DNSSEC Validator Use-After-Free via Deep Copy Pointer Overwrite Leading to DoS and Possible Remote Code Execution
Summary: CVE-2026-33278 unbound: Unbound DNSSEC Validator Use-After-Free via Deep Copy...
Keywords:
Status: NEW
Alias: CVE-2026-33278
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2481465
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-05-19 11:56 UTC by OSIDB Bzimport
Modified: 2026-05-26 14:19 UTC (History)
4 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-05-19 11:56:28 UTC 
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.
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