CVE-2026-11721

HIGH

Cache poisoning possible with label count discrepancy, RRSIG, and wildcards

Title source: cna
STIX 2.1

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.

References (3)

Core 3
Core References
Vendor Advisory vendor-advisory
CVE-2026-11721
https://kb.isc.org/docs/cve-2026-11721

Scores

CVSS v3 7.5
EPSS 0.0039
EPSS Percentile 31.2%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-1284
Status published
Products (5)
ISC/BIND 9 9.11.0 - 9.18.50
ISC/BIND 9 9.11.3-S1 - 9.18.50-S1
ISC/BIND 9 9.20.0 - 9.20.24
ISC/BIND 9 9.20.9-S1 - 9.20.24-S1
ISC/BIND 9 9.21.0 - 9.21.23
Published Jul 22, 2026
Tracked Since Jul 22, 2026