CVE-2026-77955
Possible ZONEMD verification bypass window
- State
- Published
- Severity
- 4.4 Medium
- Published
- Sep 16, 2026
- Updated
- Sep 16, 2026
- Reserved
- Sep 7, 2026
Description
In NLnet Labs Unbound 1.13.2 up to and including 1.26.1, a vulnerability in ZONEMD configured zones (zonemd-check: yes) which are located below (but not at) a trust anchor allow for an attack window where (tampered with) zone contents are served (or stored to disk) prior to the ZONEMD integrity check. This is caused by the needed DS/DNSKEY asynchronous resolution that needs to happen before the ZONEMD check completes. If a zonefile is written to disk (zonefile: option) while the ZONEMD check failed, the tampered data are reloaded on startup and available until ZONEMD verification concludes again. If verification fails, the data is not served any more but still persists on disk for future reloads.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.4 Medium | CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N | NLnet Labs |
Weaknesses
- CWE-345 Insufficient Verification of Data Authenticity
Affected Products
| Product | Versions |
|---|---|
UnboundNLnet Labs |
|
References
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.