Is CVE-2026-101337 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-101337 being exploited in the wild.

How severe is CVE-2026-101337?

Informational severity, published 14 October 2026.

Which products and versions are affected?

NLnet Labs NSD 4.10.0 to 4.15.2.

How is CVE-2026-101337 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-101337?

Check whether you run NLnet Labs NSD at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-101337: NSD stack buffer overflow in base64 RDATA parsing

CVE-2026-101337 · Severity: info · Published 2026-10-14

NSD is an authoritative DNS nameserver that processes zone files containing DNS records. A specially crafted zone file with malformed base64 data in resource records can cause NSD to write up to 64KB of attacker-controlled data onto the stack, potentially allowing remote code execution. The vulnerability requires an operator to feed a malicious zone file to NSD, such as through a provisioning system.

Technologies: NLnet Labs NSD. Vendors: NLnet Labs.

Quick answers

Is CVE-2026-101337 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-101337 being exploited in the wild.
How severe is CVE-2026-101337?: Informational severity, published 14 October 2026.
Which products and versions are affected?: NLnet Labs NSD 4.10.0 to 4.15.2.
Is there a fix for CVE-2026-101337?: Yes: fixed in NSD 4.15.3. Until then: Upgrade to NSD 4.15.3 or apply the patch from https://nlnetlabs.nl/downloads/nsd/patch_CVE-2026-101337.diff to NSD 4.15.2. Restrict zone file provisioning to trusted sources only. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-101337 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-101337?: Check whether you run NLnet Labs NSD at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: NSD 4.15.3

Upgrade to NSD 4.15.3 or apply the patch from https://nlnetlabs.nl/downloads/nsd/patch_CVE-2026-101337.diff to NSD 4.15.2. Restrict zone file provisioning to trusted sources only.

Technical details

An integer calculation error occurs when parsing base64-encoded RDATA fields that are split into pieces of 3 characters or less, causing the decoder to write 0 bytes and leading to an out-of-bounds stack buffer overwrite. The attack requires direct input of a crafted zone file to the NSD daemon. NSD 4.15.3 and a patch for 4.15.2 are available to fix this issue.

Affected products

NLnet Labs NSD 4.10.0 to 4.15.2

Timeline

2026-10-14: disclosed

References

https://www.nlnetlabs.nl/downloads/nsd/CVE-2026-101337.txt

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