Review reviewHigh

CVE-2026-11331

ISC BIND 9

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.

CVSS: 7.5
EPSS: 0.42%
CISA KEV: Not listed
Published: 2026.07.23

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.42%

Technical severityCVSS 7.5

Vulnerability overview

Affected product and versions

Product: ISC BIND 9
Affected versions: >= 9.16.0 <= 9.18.50, >= 9.20.0 <= 9.20.24, >= 9.21.0 <= 9.21.23, >= 9.16.8-S1 <= 9.18.50-S1, >= 9.20.9-S1 <= 9.20.24-S1
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that ISC BIND 9 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CWE: CWE-790