CVE-2026-18916
Received Received - Intake

NSD DNS Server TCP Throttling Denial of Service

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: NLnet Labs

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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-18916
EUVD
EUVD-2026-66348

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-191 The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability allows a remote attacker to crash the NSD server process by manipulating the TCP receive window after sending a TCP query. By repeatedly crashing the server processes, the attacker can prevent the NSD instance from responding to legitimate TCP requests, effectively denying service to all TCP clients.

Detection Guidance

Monitor NSD server logs for repeated crashes of child processes. Check for unusual TCP traffic patterns or connection drops during queries. Use network monitoring tools to detect sustained throttling of TCP receive windows.

Impact Analysis

If you rely on NSD for DNS services, this vulnerability could disrupt your DNS resolution for TCP-based queries. This may cause intermittent or complete outages for services dependent on DNS, leading to degraded performance or loss of connectivity for users.

Mitigation Strategies

Apply the latest NSD security patches immediately. Restrict TCP-based DNS queries if possible. Implement rate limiting on DNS servers to prevent abuse. Monitor server stability closely after applying fixes.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-18916. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart