CVE-2026-3104: Memory leak in code preparing DNSSEC proofs of non-existence

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-25 · updated 2026-09-01
Weakness: CWE-772

Description

A specially crafted domain can be used to cause a memory leak in a BIND resolver simply by querying this domain. This issue affects BIND 9 versions 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, and 9.20.9-S1 through 9.20.20-S1. BIND 9 versions 9.18.0 through 9.18.46 and 9.18.11-S1 through 9.18.46-S1 are NOT affected.

Affected products

ISC BIND: from 9.20.0 before 9.20.21; from 9.21.0 before 9.21.20 — fixed in 9.20.21, 9.21.20

How to fix

Upgrade to a fixed version: ISC BIND 9.20.21, 9.21.20. Check the vendor advisory for mitigations.

References

https://downloads.isc.org/isc/bind9/9.20.21
https://downloads.isc.org/isc/bind9/9.21.20
https://kb.isc.org/docs/cve-2026-3104
https://access.redhat.com/errata/RHSA-2026:6935
https://access.redhat.com/security/cve/CVE-2026-3104
https://bugzilla.redhat.com/show_bug.cgi?id=2451310
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-3104.json

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