Vulnerability · Published Aug 26, 2026 · Assigned by NLnet Labs
CVE-2026-18916Remote TCP DoS by throttling the TCP receive window
Medium 6.9
In plain English
A medium-severity security flaw in NSD from NLnet Labs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 4.0)6.9Medium
Exploit odds (30 days)0.5%top 60.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | nsd | no fix listed | DEBIAN-CVE-2026-18916 |
| Debian:13 | nsd | no fix listed | DEBIAN-CVE-2026-18916 |
| Debian:14 | nsd | 4.15.1-1 | DEBIAN-CVE-2026-18916 |
| Ubuntu:26.10 | nsd | no fix listed | UBUNTU-CVE-2026-18916 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| NLnet Labs | NSD | 3.2.11 – before 4.15.1 |
Weakness: CWE-191 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
References
- https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-18916.txt vendor-advisory