CVE-2026-13204 PUBLISHED

Unexpected exit in certain situations with NSEC and NSEC3 both present

Assigner: isc
Reserved: 24.06.2026 Published: 22.07.2026 Updated: 22.07.2026

If a provably insecure domain is covered by both an NSEC and NSEC3 record at the parent, and there exist an RRSIG for only one of these types, then BIND may exit unexpectedly with an assertion while validating this proof. 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.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	ISC
Product	BIND 9
Versions	Default: unaffected affected from 9.11.0 to 9.18.50 (incl.) affected from 9.20.0 to 9.20.24 (incl.) affected from 9.21.0 to 9.21.23 (incl.) affected from 9.11.3-S1 to 9.18.50-S1 (incl.) affected from 9.20.9-S1 to 9.20.24-S1 (incl.)

Exploits

We are not aware of any active exploits.

Workarounds

No workarounds known.

Solutions

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.26, 9.21.24, or 9.20.26-S1.

Credits

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