Cache Poisoning Vulnerability in BIND DNS Software by ISC
CVE-2026-11721

7.5HIGH

Key Information:

Vendor

Isc
Status
Bind 9
Vendor
CVE Published:
22 July 2026

Badges

👾 Exploit Exists

What is CVE-2026-11721?

A vulnerability in BIND DNS software allows an attacker to exploit a flaw wherein an attacker's zone can respond to queries with an RRSIG that has fewer labels than the zone it's associated with. This can lead to a wildcard name generation within the named resolver, inadvertently creating a false cache entry that can mislead DNS resolution processes. For the attack to be effective, the resolver must be configured with 'synth-from-dnssec yes;', which is the default setting, making numerous systems potentially vulnerable.

Affected Version(s)

BIND 9 9.11.0 <= 9.18.50

BIND 9 9.20.0 <= 9.20.24

BIND 9 9.21.0 <= 9.21.23

References

https://kb.isc.org/docs/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

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

ISC would like to thank Qifan Zhang of Palo Alto Networks for bringing this vulnerability to our attention.
.