Is CVE-2026-11721 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-11721 being exploited in the wild.

How severe is CVE-2026-11721?

High severity, with a CVSS score of 7.5, published 22 July 2026.

Which products and versions are affected?

Isc BIND 9 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23; Isc BIND 9 Supported Preview Edition 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.24-S1.

Is there a fix for CVE-2026-11721?

A patch was published on 2026-07-22: Fixed versions released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-11721 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-11721?

Check whether you run Isc BIND 9 or Isc BIND 9 Supported Preview Edition at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-11721: ISC BIND 9 cache poisoning via RRSIG label count discrepancy

CVE-2026-11721 · Severity: high · CVSS 7.5 · Published 2026-07-22

A vulnerability has been identified in BIND 9, a widely used software suite for managing the Domain Name System (DNS) on the internet. An attacker can trick the system into storing incorrect website address information in its memory, a process known as cache poisoning. This could allow an attacker to redirect users to malicious websites or disrupt normal internet traffic for organizations relying on the affected software.

Technologies: Isc BIND 9, Isc BIND 9 Supported Preview Edition. Vendors: Isc.

Quick answers

Is CVE-2026-11721 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-11721 being exploited in the wild.
How severe is CVE-2026-11721?: High severity, with a CVSS score of 7.5, published 22 July 2026.
Which products and versions are affected?: Isc BIND 9 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23; Isc BIND 9 Supported Preview Edition 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.24-S1.
Is there a fix for CVE-2026-11721?: A patch was published on 2026-07-22: Fixed versions released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-11721 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-11721?: Check whether you run Isc BIND 9 or Isc BIND 9 Supported Preview Edition at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A vulnerability exists in BIND 9's handling of DNSSEC-signed responses where an attacker's zone can respond with an RRSIG record containing a smaller number of labels than the zone itself. This discrepancy causes the 'named' process to incorrectly produce a wildcard name for a zone shorter than the attacker's zone. This behavior facilitates cache poisoning, allowing an attacker to inject arbitrary DNS data into the resolver's cache. The vulnerability requires the 'synth-from-dnssec' option to be enabled, which is the default setting. Patches are available in versions 9.20.26, 9.21.24, and 9.20.26-S1.

Affected products

ISC BIND 9 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23
ISC BIND 9 Supported Preview Edition 9.11.3-S1 through 9.18.50-S1, 9.20.9-S1 through 9.20.24-S1

Timeline

2026-07-15: other: Early Notification
2026-07-22: advisory: Public disclosure
2026-07-22: patched: Fixed versions released

References

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