CVE-2026-11721
Cache poisoning possible with label count discrepancy, RRSIG, and wildcards
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-1284 |
| Vendor | isc |
| Product | bind 9 |
| Published | Jul 22, 2026 |
Stay Ahead of the Next One
Get instant alerts for isc bind 9
Be the first to know when new high vulnerabilities affecting isc bind 9 are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
Affected Versions
ISC / BIND 9
9.11.0 ≤ 9.18.50 9.20.0 ≤ 9.20.24 9.21.0 ≤ 9.21.23 9.11.3-S1 ≤ 9.18.50-S1 9.20.9-S1 ≤ 9.20.24-S1
References
Credits
ISC would like to thank Qifan Zhang of Palo Alto Networks for bringing this vulnerability to our attention.