CVE-2026-12246 Out of bounds stack write with crafted APL RR
A crafted APL resource record causes a stack buffer overflow in NSD during zone writing, potentially allowing remote code execution or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12246?
CVE-2026-12246 is a high-severity memory corruption vulnerability in NLnet Labs NSD, published on 25 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
NSD version 4.14.0 introduced a bug where a specially crafted APL RR, with an adflength larger than permitted for the address family will overwrite the stack when the zone is written to disk, with a maximum of 111 attacker controlled bytes.
Which versions are affected by CVE-2026-12246?
It affects 1 product.
Products include Nlnetlabs Nsd.
How do I fix CVE-2026-12246?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-12246 being exploited?
There is no known exploitation of CVE-2026-12246 in the wild and no public exploit code.
Other vulnerabilities in NLnet Labs NSD
- CVE-2026-12244 Heap overflow and crash with crafted SVCB RR
- CVE-2026-12245 Denial of DNS over TLS service by any DoT client
- CVE-2026-18664 Wrong interpretation of ACL ranges
- CVE-2026-19401 Remote UDP DoS by sending multiple DNS Cookie options
- CVE-2026-19538 Bypass of BLOCKED ACL items on proxy protocol port over TCP or TLS
Sources
Also known as ALPINE-CVE-2026-12246, DEBIAN-CVE-2026-12246, GHSA-xgm5-85mh-3559.