It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default).
This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.
This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ISC | BIND 9 | unaffected |
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Advisories
No advisories yet.
Fixes
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.
References
History
Wed, 22 Jul 2026 15:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels than the zone in which the RRSIG is contained. This causes `named` to produce a wildcard name for a zone that is shorter than the attacker's zone, which can result in cache poisoning. For this attack to have any effect, the resolver under attack must have set `synth-from-dnssec yes;` (which is the default). This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1. | |
| Title | Cache poisoning possible with label count discrepancy, RRSIG, and wildcards | |
| First Time appeared |
Isc
Isc bind |
|
| Weaknesses | CWE-1284 | |
| CPEs | cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Isc
Isc bind |
|
| References |
| |
| Metrics |
cvssV3_1
|
Projects
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MITRE
Status: PUBLISHED
Assigner: isc
Published:
Updated: 2026-07-22T14:13:08.748Z
Reserved: 2026-06-09T01:19:47.697Z
Link: CVE-2026-11721
Vulnrichment
No data.
NVD
No data.
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses