BIND 9 'named' Crash on DNAME/A Record Race (9.18.x-9.20.x)
CVE-2026-12617 Published on July 22, 2026
Record ordering based unexpected exit with CNAME or DNAME
The issue is unexpected program termination based on ordering and/or specific content in responses to queries for CNAME or DNAME, and A records. Specifically, if a client queries for a DNAME and A record below the DNAME to the resolver, and the authoritative server responds positively to the A query but delays the DNAME response and later responds negatively, `named` may quit unexpectedly. Or, if a client queries for a CNAME and A record for the same name to the resolver, and the authoritative server responds positively to the A query but delays the CNAME response and later responds with a self-referential CNAME, the same failure may occur.
This issue affects BIND 9 versions 9.18.0 through 9.18.50, 9.20.0 through 9.20.24, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.
Vulnerability Analysis
CVE-2026-12617 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is an assertion failure Vulnerability?
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
CVE-2026-12617 has been classified to as an assertion failure vulnerability or weakness.
Products Associated with CVE-2026-12617
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Affected Versions
ISC BIND 9:- Version 9.18.0, <= 9.18.50 is affected.
- Version 9.20.0, <= 9.20.24 is affected.
- Version 9.18.11-S1, <= 9.18.50-S1 is affected.
- Version 9.20.9-S1, <= 9.20.24-S1 is affected.