CVE-2026-18916 Remote TCP DoS by throttling the TCP receive window
Remote attackers can crash NSD server children by throttling TCP receive windows, causing denial of service for TCP queries.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-18916?
CVE-2026-18916 is a medium-severity denial of service vulnerability in NLnet Labs NSD, published on 26 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Any remote client can crash a NSD serve child, by throttling the TCP receive window after a TCP query. By continuously crashing the serve childs, the remote client can denial all TCP service to this NSD instance.
Weakness: CWE-191
Which versions are affected by CVE-2026-18916?
It affects 1 product.
Products include Nlnetlabs Nsd.
How do I fix CVE-2026-18916?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-18916 being exploited?
There is no known exploitation of CVE-2026-18916 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 DEBIAN-CVE-2026-18916, GHSA-m6mr-q7j3-3rc6, UBUNTU-CVE-2026-18916.