Possible arbitrary code execution during DNSSEC validation (NLnet Labs Unbound)
At a glance
- Source
- NVD
- EPSS
- EPSS 1.42 % · percentile 73 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- NLnet Labs
- NVD status
- Modified
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.
Weaknesses (CWE)
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt
- https://access.redhat.com/security/cve/CVE-2026-33278
- https://bugzilla.redhat.com/show_bug.cgi?id=2479808
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33278.json
- https://access.redhat.com/errata/RHSA-2026:23231
- https://access.redhat.com/errata/RHSA-2026:24369
- https://access.redhat.com/errata/RHSA-2026:19752
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 4.0 | CRITICAL 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 | NLnet Labs |
| CVSS 3.1 | HIGH 8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H | redhat-SADP |
| CVSS 4.0 | CRITICAL 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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Red | NVD · sep@nlnetlabs.nl (Secondary) |
| CVSS 3.1 | CRITICAL 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | NVD · nvd@nist.gov (Primary) |
| CVSS 3.1 | HIGH 8.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H | NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary) |
European references
- ENISA EUVD · EUVD-2026-31075
- GCVE · GCVE-0-2026-33278
CERT-FR advisories
- CERTFR-2026-AVI-1111 — Multiples vulnérabilités dans les produits F5 · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*≥ 1.19.1 < 1.25.1
Affected products
| Product | Versions |
|---|---|
| NLnet Labs · Unbound | affected 1.19.1 < 1.25.1 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |