CVE-2026-33278 Affecting unbound package, versions <1.22.0-2+deb13u3


Severity

Recommended
0.0
critical
0
10

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Threat Intelligence

EPSS
1.27% (67th percentile)

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  • Snyk IDSNYK-ECHOLATEST-UNBOUND-18234967
  • published23 Jul 2026
  • disclosed20 May 2026

Introduced: 20 May 2026

CVE-2026-33278  (opens in a new tab)

How to fix?

Upgrade Echo:latest unbound to version 1.22.0-2+deb13u3 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound package and not the unbound package as distributed by Echo. See How to fix? for Echo:latest relevant fixed versions and status.

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 Base Scores

version 3.1