CVE-2026-11331

Potential wildcard CNAME RPZ policy bypass

State: Published
Severity: 7.5 High
Published: Jul 22, 2026
Updated: Jul 22, 2026
Reserved: Jun 5, 2026

Description

An attacker who knows (or guesses) that a resolver uses RPZ with wildcard CNAME policies can craft query names long enough to trigger a NAMETOOLONG error condition during RPZ processing. This is not handled correctly and may lead to defeating the RPZ rule. It also may lead to an unexpected exit of the BIND 9 software. This issue affects BIND 9 versions 9.16.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.16.8-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N	isc

Weaknesses

CWE-790 Improper Filtering of Special Elements

Affected Products

Product	Versions
BIND 9ISC	9.16.0 through 9.18.50Affected 9.20.0 through 9.20.24Affected 9.21.0 through 9.21.23Affected 9.16.8-S1 through 9.18.50-S1Affected 9.20.9-S1 through 9.20.24-S1Affected

References

CVE-2026-11331vendor-advisory
https://downloads.isc.org/isc/bind9/9.20.26patch
https://downloads.isc.org/isc/bind9/9.21.24patch

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