CVE-2026-19667

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

Published Sep 16, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
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.

Remediation

Vendor Solution

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.29, 9.21.26, or 9.20.29-S1.


Vendor Workaround

No workarounds known.

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4865-1 bind9 security update
Debian DSA Debian DSA DSA-6505-1 bind9 security update
Ubuntu USN Ubuntu USN USN-8929-1 Bind vulnerabilities
Ubuntu USN Ubuntu USN USN-8969-1 Bind vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Isc bind 9
Vendors & Products Isc bind 9
Type Values Removed Values Added
Description 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.
Title Remote assertion failure via 16-bit length truncation in `dns_ncache_add()`
First Time appeared Isc
Isc bind
Weaknesses CWE-197
CPEs cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
Vendors & Products Isc
Isc bind
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
isc
Published
Updated
Sep 17, 2026, 6:45 PM
Reserved
Aug 12, 2026, 8:29 PM
Status
Awaiting Analysis
Published
Sep 16, 2026, 2:17 PM
Modified
Oct 26, 2026, 8:10 PM
Severity
Important
Public date
Sep 16, 2026, 1:46 PM