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Vulnerability record · CVE-2026-11721 · published 22 July 2026

CVE-2026-11721: It is possible for an attacker's zone to respond to a query with an RRSIG that has a smaller number of labels …

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.

7.5 CVSS 3.1 High EPSS 0.40% · top 68.9% CWE-1284 · CWE-1284 Undergoing Analysis
7.5CVSS 3.1 base score
0.40%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
22 Jul 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

LinkTags
https://downloads.isc.org/isc/bind9/9.20.26
https://downloads.isc.org/isc/bind9/9.21.24
https://kb.isc.org/docs/cve-2026-11721

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Source: NIST National Vulnerability Database (record CVE-2026-11721), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.