Vulnerability 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.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nlnetlabs | Unbound | >= 1.19.1, < 1.25.1 |
Related Weaknesses (CWE)
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txtMitigationVendor Advisory
FAQ
What is CVE-2026-33278?
CVE-2026-33278 is a vulnerability with a CVSS score of 9.8 (CRITICAL). 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...
How severe is CVE-2026-33278?
CVE-2026-33278 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-33278?
Check the references section above for vendor advisories and patch information. Affected products include: Nlnetlabs Unbound.