Description
If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure. This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.
Scores
CVSS v3
7.5
EPSS
0.0003
EPSS Percentile
7.2%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-617
Status
published
Products (5)
ISC/BIND 9
9.18.0 - 9.18.37
ISC/BIND 9
9.18.11-S1 - 9.18.37-S1
ISC/BIND 9
9.20.0 - 9.20.10
ISC/BIND 9
9.20.9-S1 - 9.20.10-S1
ISC/BIND 9
9.21.0 - 9.21.9
Published
Jul 16, 2025
Tracked Since
Feb 18, 2026