CVE-2026-101337: Stack-Based Buffer Overflow Flaw in NLnet Labs NSD Scores 8.7 on CVSS
A newly published high vulnerability in NLnet Labs NSD carries a CVSS score of 8.7. Here is what is affected and how to respond.
Key points
- CVE-2026-101337 affects NLnet Labs NSD.
- CVSS 8.7 (High).
- No exploitation confirmed yet.
NLnet Labs NSD is affected by CVE-2026-101337, a stack-based buffer overflow that the National Vulnerability Database rates 8.7 out of 10.
At a glance
- CVE
- CVE-2026-101337
- Product
- NLnet Labs NSD
- CVSS
- 8.7 High
- Weakness
- stack-based buffer overflow
- Exploited
- No known exploitation
What is the vulnerability?
The NVD entry states: When base64 data is split up in pieces, of 3 character or less, tokens were incorrectly calculated to produce 0 bytes. This enables attackers to overwrite the stack with up to 64K of attacker controlled data. Zone files which are written out by NSD itself, such as for zones for which the NSD instance is secondary, will not be formatted like this. The zone file must be fed to NSD directly, (but it could come, for example, from an operator controlled provisioning system).
Affected versions
| Vendor | Product | Versions |
|---|---|---|
| Nlnet Labs | NSD | before 4.15.3 |
Is it being exploited?
There is no public confirmation of exploitation at the time of publication. It does not appear in CISA's Known Exploited Vulnerabilities catalog. We will update this report if that changes.
What should you do?
- Identify whether the affected product and versions run in your environment.
- Apply the vendor update listed in the advisory as soon as it is available.
- Limit network exposure of the affected service until it is patched.
- Monitor the vendor advisory for updated guidance or exploitation reports.
What to do and how to stay safe: CVE-2026-101337
- Vulnerability severity scores ignore your specific architecture and context.
- Exploitability depends on network exposure and user behavior, not just code flaws.
- Prioritization requires continuous asset inventory and threat intelligence alignment.
Risk-based vulnerability management focuses your limited resources on the flaws that actually threaten your business. Start by mapping your critical assets and checking for active exploits to prioritize your backlog.
Step-by-step guide: Risk-Based Vulnerability Management: Prioritize Fixes by Actual Danger
General security guidance from the Threat Times newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is CVE-2026-101337?
CVE-2026-101337 is a stack-based buffer overflow vulnerability in NLnet Labs NSD.
How severe is CVE-2026-101337?
It has a CVSS score of 8.7 High.
Is CVE-2026-101337 being exploited?
There is no public confirmation of exploitation at the time of publication.
