CVE-2026-12246
Received Received - Intake
Stack Overflow in NSD Due to Malformed APL RR

Publication date: 2026-06-25

Last updated on: 2026-06-25

Assigner: NLnet Labs

Description
NSD version 4.14.0 introduced a bug where a specially crafted APL RR, with an adflength larger than permitted for the address family will overwrite the stack when the zone is written to disk, with a maximum of 111 attacker controlled bytes.
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Meta Information
Published
2026-06-25
Last Modified
2026-06-25
Generated
2026-06-25
AI Q&A
2026-06-25
EPSS Evaluated
N/A
NVD
CVE-2026-12246
EUVD
EUVD-2026-39184
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
nlnetlabs nsd From 4.14.0 (inc) to 4.14.2 (inc)
nlnetlabs nsd 4.14.3
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-120 The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
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Executive Summary

CVE-2026-12246 is a vulnerability in NSD versions 4.14.0 through 4.14.2 involving an out-of-bounds stack write. It occurs when a specially crafted APL resource record (RR) contains an address length larger than allowed for its address family. When the zone file is written to disk, this malformed APL RR causes up to 111 attacker-controlled bytes to overwrite the stack.

This happens due to improper handling of the APL RR's address length during zone file serialization, leading to a buffer overflow on the stack.

Impact Analysis

The vulnerability can allow an attacker to overwrite parts of the stack with controlled data, which may lead to unpredictable behavior, crashes, or potentially enable code execution depending on the context.

It is particularly significant in multi-tenant secondary DNS deployments where a malicious primary server within NSD's trust boundary could introduce a harmful APL record that the secondary server processes, potentially compromising the secondary DNS server.

Detection Guidance

This vulnerability involves a specially crafted APL resource record (RR) with an address length exceeding the permitted size for its address family, which causes a stack overwrite when the zone is written to disk.

Detection would involve inspecting zone files for APL RRs that have an adflength larger than allowed. However, no specific detection commands or tools are provided in the available resources.

Mitigation Strategies

To mitigate this vulnerability, users should upgrade NSD to version 4.14.3, which includes a patch fixing the issue.

Alternatively, if using NSD 4.14.2, a manual patch is available. The patch file can be downloaded and applied to the NSD source directory using the command 'patch -p1', followed by reinstalling NSD with 'make install'.

Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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