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.
Published: 2026-08-26
Score: 6.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service via remote TCP receive window throttling
Action: Patch Now
AI Analysis

Impact

A remote client can crash an NSD child process by throttling the TCP receive window after a query. The child crash leads to a brief service interruption, and repeated crashes can render the NSD instance unable to serve any TCP traffic. The flaw corresponds to integer-related overflow or underflow weaknesses (CWE-191).

Affected Systems

The affected product is NLnet Labs NSD. Versions prior to 4.15.1 are vulnerable; the fix is included in 4.15.1 and later releases.

Risk and Exploitability

The CVSS score of 6.9 indicates a moderate severity. EPSS data is not available, and the vulnerability is not listed in the CISA KEV catalog, suggesting no known broad exploitation yet. However, the flaw is exploitable from a remote host that can send crafted DNS queries over TCP. The attack requires no special credentials, making it straightforward for an adversary to mount a denial‑of‑service attack.

Generated by OpenCVE AI on August 26, 2026 at 09:21 UTC.

Remediation

Vendor Solution

This issue is fixed in 4.15.1 and all later versions.

OpenCVE Recommended Actions

  • Upgrade NSD to version 4.15.1 or newer to apply the official fix
  • If an upgrade cannot occur immediately, use firewall rules to rate‑limit or block excessive TCP connections to the NSD port to reduce the likelihood of triggering the crash
  • Configure the NSD service to automatically restart on failure or use a watchdog to ensure service continuity during crash periods

Generated by OpenCVE AI on August 26, 2026 at 09:21 UTC.

Tracking

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Advisories

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History

Tue, 08 Sep 2026 20:15:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:nlnetlabs:nsd:*:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Tue, 01 Sep 2026 14:45:00 +0000

Type Values Removed Values Added
First Time appeared Nlnetlabs
Nlnetlabs nsd
Vendors & Products Nlnetlabs
Nlnetlabs nsd

Wed, 26 Aug 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 26 Aug 2026 08:45:00 +0000

Type Values Removed Values Added
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.
Title Remote TCP DoS by throttling the TCP receive window
Weaknesses CWE-191
References
Metrics cvssV4_0

{'score': 6.9, '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'}

Subscriptions

Nlnetlabs Nsd
cve-icon MITRE

Status: PUBLISHED

Assigner: NLnet Labs

Published:

Updated: 2026-08-26T14:22:31.309Z

Reserved: 2026-08-05T07:36:55.457Z

Link: CVE-2026-18916

cve-icon Vulnrichment

Updated: 2026-08-26T14:22:27.071Z

cve-icon NVD

Status : Analyzed

Published: 2026-08-26T09:16:45.597

Modified: 2026-09-08T20:00:51.850

Link: CVE-2026-18916

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-01T14:24:26Z

Weaknesses
  • CWE-191

    Integer Underflow (Wrap or Wraparound)