CVE-2026-11331 PUBLISHED

Potential wildcard CNAME RPZ policy bypass

Assigner: isc
Reserved: 05.06.2026 Published: 22.07.2026 Updated: 22.07.2026

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.

Metrics

CVSS 3.1

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

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	ISC
Product	BIND 9
Versions	Default: unaffected affected from 9.16.0 to 9.18.50 (incl.) affected from 9.20.0 to 9.20.24 (incl.) affected from 9.21.0 to 9.21.23 (incl.) affected from 9.16.8-S1 to 9.18.50-S1 (incl.) affected from 9.20.9-S1 to 9.20.24-S1 (incl.)

Exploits

We are not aware of any active exploits.

Workarounds

No workarounds known.

Solutions

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.26, 9.21.24, or 9.20.26-S1.

Credits

ISC would like to thank Laith Mash'al (0xmshal) for bringing this vulnerability to our attention.

References

Problem Types

CWE-790 Improper Filtering of Special Elements CWE

Impacts

If such a situation is encountered, the targeted RPZ rule may be bypassed. The condition could also lead to an unexpected exit.