# CVE-2026-33278

## Summary

- **CVE ID:** CVE-2026-33278
- **Severity:** CRITICAL
- **CVSS Score:** 9.1 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red)
- **CWE:** CWE-416, CWE-672
- **Published:** May 20, 2026
- **Last Modified:** Sep 1, 2026

## 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.

## Affected Products

- NLnet Labs — Unbound (1.19.1)

## References

- [CNA](https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt)
- [redhat-SADP](https://access.redhat.com/security/cve/CVE-2026-33278)
- [redhat-SADP](https://bugzilla.redhat.com/show_bug.cgi?id=2479808)
- [redhat-SADP](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33278.json)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:23231)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:24369)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:19752)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 1.27%
- **EPSS Percentile:** 68.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._