Vulnerability · Published Jul 22, 2026 · Assigned by isc
CVE-2026-11721Cache poisoning possible with label count discrepancy, RRSIG, and wildcards
High 7.5
In plain English
A high-severity security flaw in BIND 9 from ISC. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.4%top 66.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | bind | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:8 | bind | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | bind | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:10 | bind-chroot | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:8 | bind-chroot | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | bind-chroot | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:10 | bind-devel | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:8 | bind-devel | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | bind-devel | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:9 | bind-dnssec-doc | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:10 | bind-dnssec-utils | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:9 | bind-dnssec-utils | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:10 | bind-doc | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:9 | bind-doc | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:8 | bind-export-devel | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-export-libs | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:10 | bind-libs | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:8 | bind-libs | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | bind-libs | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:8 | bind-libs-lite | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:10 | bind-license | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:8 | bind-license | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | bind-license | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:8 | bind-lite-devel | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-pkcs11 | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-pkcs11-devel | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-pkcs11-libs | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-pkcs11-utils | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-sdb | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:8 | bind-sdb-chroot | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:10 | bind-utils | 32:9.18.33-15.el10_2.10 | ALSA-2026:55437 |
| AlmaLinux:8 | bind-utils | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | bind-utils | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:8 | bind9.16 | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-chroot | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-devel | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-dnssec-utils | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-doc | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-libs | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-license | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:8 | bind9.16-utils | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| AlmaLinux:9 | bind9.18 | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:9 | bind9.18-chroot | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:9 | bind9.18-devel | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:9 | bind9.18-dnssec-utils | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:9 | bind9.18-doc | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:9 | bind9.18-libs | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:9 | bind9.18-utils | 32:9.18.29-14.el9_8.8 | ALSA-2026:55442 |
| AlmaLinux:8 | python3-bind | 32:9.11.36-16.el8_10.14 | ALSA-2026:54654 |
| AlmaLinux:9 | python3-bind | 32:9.16.23-40.el9_8.8 | ALSA-2026:54510 |
| AlmaLinux:8 | python3-bind9.16 | 32:9.16.23-0.22.el8_10.12 | ALSA-2026:54509 |
| Alpine:v3.22 | bind | 9.20.26-r0 | ALPINE-CVE-2026-11721 |
| Alpine:v3.23 | bind | 9.20.26-r0 | ALPINE-CVE-2026-11721 |
| Alpine:v3.24 | bind | 9.20.26-r0 | ALPINE-CVE-2026-11721 |
| Debian:12 | bind9 | 1:9.18.49-1~deb12u2 | DEBIAN-CVE-2026-11721 |
| Debian:13 | bind9 | 1:9.20.26-1~deb13u1 | DEBIAN-CVE-2026-11721 |
| Debian:14 | bind9 | 1:9.20.26-1 | DEBIAN-CVE-2026-11721 |
| Rocky Linux:10 | bind | 2:9.18.33-15.el10_2.10 | RLSA-2026:55437 |
| Rocky Linux:8 | bind | 2:9.11.36-16.el8_10.14 | RLSA-2026:54654 |
| Rocky Linux:9 | bind | 2:9.16.23-40.el9_8.8 | RLSA-2026:54510 |
| Rocky Linux:8 | bind9.16 | 2:9.16.23-0.22.el8_10.12 | RLSA-2026:54509 |
| Rocky Linux:9 | bind9.18 | 2:9.18.29-14.el9_8.8 | RLSA-2026:55442 |
| Ubuntu:22.04:LTS | bind9 | 1:9.18.39-0ubuntu0.22.04.5 | USN-8648-1 |
| Ubuntu:22.04:LTS | bind9 | 1:9.18.39-0ubuntu0.22.04.7 | USN-8929-1 |
| Ubuntu:22.04:LTS | bind9 | 1:9.18.39-0ubuntu0.22.04.5 | UBUNTU-CVE-2026-11721 |
| Ubuntu:24.04:LTS | bind9 | 1:9.18.39-0ubuntu0.24.04.6 | USN-8648-1 |
| Ubuntu:24.04:LTS | bind9 | 1:9.18.39-0ubuntu0.24.04.8 | USN-8929-1 |
| Ubuntu:24.04:LTS | bind9 | 1:9.18.39-0ubuntu0.24.04.6 | UBUNTU-CVE-2026-11721 |
| Ubuntu:26.04:LTS | bind9 | 1:9.20.24-1ubuntu0.2 | USN-8648-1 |
| Ubuntu:26.04:LTS | bind9 | 1:9.20.24-1ubuntu0.4 | USN-8929-1 |
| Ubuntu:26.04:LTS | bind9 | 1:9.20.24-1ubuntu0.2 | UBUNTU-CVE-2026-11721 |
| Ubuntu:22.04:LTS | bind9-libs | no fix listed | UBUNTU-CVE-2026-11721 |
| Ubuntu:24.04:LTS | isc-dhcp | no fix listed | UBUNTU-CVE-2026-11721 |
| Ubuntu:26.04:LTS | isc-dhcp | no fix listed | UBUNTU-CVE-2026-11721 |
Affected products (as reported)
Weakness: CWE-1284 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
References
- CVE-2026-11721 vendor-advisory
- https://downloads.isc.org/isc/bind9/9.20.26 patch
- https://downloads.isc.org/isc/bind9/9.21.24 patch