High [CVE-2026-11721] Cache poisoning via label count discrepancy, RRSIG, wildcards
This high-severity Red Hat Linux advisory covers CVE-2026-11721 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8.
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Summary
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.
Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N). Weakness: CWE-345.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 7 Extended Lifecycle Support; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions; Red Hat Enterprise Linux 9.6 Extended Update Support; Red Hat OpenShift Container Platform 4.22; Red Hat Hardened Images; Red Hat Enterprise Linux 6.
Red Hat lists Red Hat Enterprise Linux 9 as not affected. Red Hat fixing advisory: RHSA-2026:55437, RHSA-2026:60383, RHSA-2026:54509, RHSA-2026:54654, RHSA-2026:54510, RHSA-2026:55442, RHSA-2026:57189, RHSA-2026:55441, RHSA-2026:57362, RHSA-2026:54071.
- 9.11.0
- 9.18.50
- 9.20.0
- 9.20.24
- 9.21.0
- 9.21.23
- 9.11.3
- 9.20.9
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
- bind-32:9.18.33-15.el10_2.10
- bind-32:9.11.4-26.P2.el7_9.21
- bind9.16-32:9.16.23-0.22.el8_10.12
- bind-32:9.11.36-16.el8_10.14
- bind-32:9.16.23-40.el9_8.8
- bind9.18-32:9.18.29-14.el9_8.8
- bind-32:9.16.23-18.el9_4.12
- bind-32:9.16.23-31.el9_6.4
- rhcos-4.22.9.8.202608191915-0
- bind-main-9.20.26-0.1.hum1
- RHSA-2026:55437
- RHSA-2026:60383
- RHSA-2026:54509
- RHSA-2026:54654
- RHSA-2026:54510
- RHSA-2026:55442
- RHSA-2026:57189
- RHSA-2026:55441
- RHSA-2026:57362
- RHSA-2026:54071
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
Mitigation
Upgrade to a fixed release: bind-32:9.18.33-15.el10_2.10, bind-32:9.11.4-26.P2.el7_9.21, bind9.16-32:9.16.23-0.22.el8_10.12, bind-32:9.11.36-16.el8_10.14, bind-32:9.16.23-40.el9_8.8, bind9.18-32:9.18.29-14.el9_8.8. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
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