CVE-2026-77119

NSEC3 insecure-referral proof can use unrelated cached NSEC3 RRsets

State: Published
Severity: 5.9 Medium
Published: Sep 16, 2026
Updated: Sep 17, 2026
Reserved: Aug 20, 2026

Description

A validly signed NSEC3 from an unrelated sibling zone may be accepted as an insecurity proof, downgrading a secure delegation and letting a forged unsigned answer through. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

Scores

CVSS	Score	Vector	Source
3.1	5.9 Medium	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N	isc

Weaknesses

CWE-346 Origin Validation Error

Affected Products

Product	Versions
BIND 9ISC	9.11.0 through 9.18.50Affected 9.20.0 through 9.20.27Affected 9.21.0 through 9.21.25Affected 9.11.3-S1 through 9.18.50-S1Affected 9.20.9-S1 through 9.20.27-S1Affected

References

CVE-2026-77119vendor-advisory
https://downloads.isc.org/isc/bind9/9.20.29patch
https://downloads.isc.org/isc/bind9/9.21.26patch

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