CVE-2026-19667

HIGH 7.5

Remote assertion failure via 16-bit length truncation in `dns_ncache_add()`

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

If an attacker-controlled authoritative server can produce a negative answer that is exactly 65536 bytes, then a flaw in `named` results in a negative cache entry of 0 bytes. When this entry is subsequently read, `named` aborts. 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.

CWE	CWE-197
Vendor	isc
Product	bind 9
Published	Sep 16, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

ISC / BIND 9

9.11.0 ≤ 9.18.50 9.20.0 ≤ 9.20.27 9.21.0 ≤ 9.21.25 9.11.3-S1 ≤ 9.18.50-S1 9.20.9-S1 ≤ 9.20.27-S1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

kb.isc.org: https://kb.isc.org/docs/cve-2026-19667 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.20.29 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.21.26

Credits

ISC would like to thank Rintaro Kawasugi for bringing this vulnerability to our attention.