CVE-2026-77955 (GCVE-0-2026-77955)

Vulnerability from cvelistv5 – Published: 2026-09-16 08:29 – Updated: 2026-09-16 14:33
VLAI
Title
Possible ZONEMD verification bypass window
Summary
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.
Severity
4.4 (Medium)
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 14:33 UTC
CWE
  • CWE-345 - Insufficient Verification of Data Authenticity
Assigner
NLnet Labs CNA
CNA scorecard B 82/100 over 76 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
NLnet Labs Unbound Affected: 1.13.2 , < 1.26.1 (semver)
guessed Create a notification for this product.
Date Public
2026-09-16 00:00
Credits
Yuqi Qiu (Nankai University, AOSP Lab) Xiang Li (Nankai University, AOSP Lab) Qifan Zhang (Palo Alto Networks)
Show details on NVD website
To clipboard 

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