NLnet Labs NSD up to 4.15.2 Base64 Decoder stack-based overflow

Summaryinfo

A vulnerability identified as very critical has been detected in NLnet Labs NSD up to 4.15.2. The affected element is an unknown function of the component Base64 Decoder. Performing a manipulation results in stack-based overflow. This vulnerability is cataloged as CVE-2026-101338. It is possible to initiate the attack remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as very critical, was found in NLnet Labs NSD up to 4.15.2. This affects some unknown functionality of the component Base64 Decoder. The manipulation with an unknown input leads to a stack-based overflow vulnerability. CWE is classifying the issue as CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

When a SVCB or HTTPS RR has filled the wire format RDATA up to the brim, another ECH parameter may overwrite the stack, and once beyond the limit, the base64 decoder can write attacker controlled data of unlimited size. 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).

It is possible to read the advisory at nlnetlabs.nl. This vulnerability is uniquely identified as CVE-2026-101338 since 09/28/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/14/2026).

Upgrading to version 4.15.3 eliminates this vulnerability.

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Productinfo

Type

• Domain Name Software

Vendor

• NLnet Labs

Name

• NSD

Version

• 4.15.0
• 4.15.1
• 4.15.2

CPE 2.3info

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CPE 2.2info

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