CVE-2026-19667 Remote assertion failure via 16-bit length truncation in `dns_ncache_add()`
A remote attacker can cause a denial of service in BIND by triggering an assertion failure via a specific negative DNS response size.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-19667?
CVE-2026-19667 is a high-severity vulnerability in ISC BIND 9, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-197
Which versions are affected by CVE-2026-19667?
How do I fix CVE-2026-19667?
Apply the vendor's patch.
Is CVE-2026-19667 being exploited?
There is no known exploitation of CVE-2026-19667 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-19667, AZL-103329, BELL-CVE-2026-19667, CLSA-2026-1790352528, CLSA-2026-1790352942, DEBIAN-CVE-2026-19667 and 6 more.