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CVE-2026-11331

Potential wildcard CNAME RPZ policy bypass

High7.5EPSS 0.43%
Published
Updated
Reserved
Assigned by
isc

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 scores of CVE-2026-11331, by who scored it
Scored byCVSSScoreVector
iscCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVDNVD · Analyzed3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (exploitation in 30 days)
0.43% · top 63% of all CVEs (4 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

  • ISC · BIND 9

    • affected 9.16.0 – ≤ 9.18.50
    • affected 9.20.0 – ≤ 9.20.24
    • affected 9.21.0 – ≤ 9.21.23
    • affected 9.16.8-S1 – ≤ 9.18.50-S1
    • affected 9.20.9-S1 – ≤ 9.20.24-S1

What to do

Solution: 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.

Workaround: No workarounds known.

Exploitation: We are not aware of any active exploits.

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .