RPZ policy bypass via overlong wildcard expansion
Published Jul 22, 2026 · Updated Jul 22, 2026
Improper filtering in BIND 9 allows remote attackers to bypass wildcard CNAME RPZ rules via overlong DNS query names. During RPZ processing, an overlong wildcard CNAME expansion raises NAMETOOLONG, yet named returns a self-referential CNAME and the original address instead of rejecting the name. The resolver must use a wildcard CNAME RPZ policy; the query can defeat that policy, and branches through 9.20 can also terminate on an assertion failure.
Summary
What happened
Improper filtering in BIND 9 allows remote attackers to bypass wildcard CNAME RPZ rules via overlong DNS query names. During RPZ processing, an overlong wildcard CNAME expansion raises NAMETOOLONG, yet named returns a self-referential CNAME and the original address instead of rejecting the name. The resolver must use a wildcard CNAME RPZ policy; the query can defeat that policy, and branches through 9.20 can also terminate on an assertion failure.
The record
- CVE
- CVE-2026-11331
- Published
- Jul 22, 2026
- Updated
- Jul 22, 2026
- Vendor
- Internet Systems Consortium
- Product
- BIND 9
- Classifications
- CWE-790
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 22, 2026CVE publishedPublication date reported by the CVE source.
- Jul 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
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Is a vulnerable build present?
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- Affected versionversion=9.16.0 <=9.18.50
- Affected versionversion=9.16.8-S1 <=9.18.50-S1
- Affected versionversion=9.20.0 <=9.20.24
- Affected versionversion=9.20.9-S1 <=9.20.24-S1
- Affected versionversion=9.21.0 <=9.21.23
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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Your stack
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