CVE-2026-33278
Description
NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's 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. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
23- osv-coords20 versionspkg:rpm/almalinux/python3-unboundpkg:rpm/almalinux/unboundpkg:rpm/almalinux/unbound-anchorpkg:rpm/almalinux/unbound-develpkg:rpm/almalinux/unbound-dracutpkg:rpm/almalinux/unbound-libspkg:rpm/almalinux/unbound-utilspkg:rpm/opensuse/unbound&distro=openSUSE%20Tumbleweedpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP4-ESPOSpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP4-LTSSpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP5-ESPOSpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP5-LTSSpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Micro%205.5pkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP4-LTSSpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP5-LTSSpkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Server%2016.0pkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015%20SP4pkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015%20SP5pkg:rpm/suse/unbound&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20applications%2016.0pkg:rpm/suse/unbound&distro=SUSE%20Linux%20Micro%206.2
< 1.24.2-7.el10_2.1+ 19 more
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.24.2-7.el10_2.1
- (no CPE)range: < 1.25.1-1.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.24.1-160000.2.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.20.0-150100.10.25.1
- (no CPE)range: < 1.24.1-160000.2.1
- (no CPE)range: < 1.24.1-160000.2.1
Patches
Vulnerability mechanics
References
1- www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txtnvdMitigationVendor Advisory
News mentions
1- NLnet Labs Unbound: 11 CVEs Disclosed in Single Advisory — Two Critical Including Cache PoisoningVypr Intelligence · May 20, 2026