CVE-2026-12245 Denial of DNS over TLS service by any DoT client
A heap use-after-free in NSD allows remote attackers to crash the DNS over TLS service by closing connections prematurely.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12245?
CVE-2026-12245 is a high-severity use after free vulnerability in NLnet Labs NSD, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
NSD from version 4.13.0 has a heap use-after-free bug in logging errors on TLS connections, causing a crash of the server process, which can be triggered trivially by sending a DNS query over a DoT connection, and closing the connection without reading the response.
Weakness: CWE-416
Which versions are affected by CVE-2026-12245?
It affects 1 product.
Products include Nlnetlabs Nsd.
How do I fix CVE-2026-12245?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-12245 being exploited?
There is no known exploitation of CVE-2026-12245 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-2026-18664 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
- CVE-2026-12490 Bypass of client certificate verification with transfer over TLS
Sources
Also known as ALPINE-CVE-2026-12245, DEBIAN-CVE-2026-12245, GHSA-rcp9-2p4r-m2hm.