CVE-2026-6069: NASM stack buffer overflow in disasm function

CVE-2026-6069 · Severity: high · CVSS 7.5 · Published 2026-04-10

The Netwide Assembler (NASM), a widely used tool for translating assembly code into machine-readable formats, contains a security vulnerability in its disassembly function. An attacker can provide specially crafted input that causes the software to crash or behave unpredictably by overflowing its internal memory buffers. This could lead to a denial-of-service, impacting the availability of automated build or analysis pipelines that rely on NASM.

Technologies: Nasm Netwide Assembler. Vendors: Nasm.

Quick answers

Is CVE-2026-6069 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-6069 being exploited in the wild.
How severe is CVE-2026-6069?
High severity, with a CVSS score of 7.5, published 10 April 2026.
Which products and versions are affected?
NASM Netwide Assembler (NASM) 3.02:rc5.
Is there a fix for CVE-2026-6069?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-6069 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-6069?
Check whether you run Nasm Netwide Assembler. 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.

Technical details

A stack-based buffer overflow (CWE-787) exists in the disasm() function within disasm/disasm.c of the Netwide Assembler (NASM). The vulnerability is caused by the function mixing bounded snprintf() calls with direct memory writes (e.g., memcpy and direct array indexing) that fail to validate the remaining capacity of the caller-provided output buffer. When the length of the formatted disassembly string (slen) exceeds the buffer capacity (outbufsize), an out-of-bounds write occurs, specifically at the null-termination step (output[slen] = '\0'). An attacker can exploit this by providing input that generates long disassembly strings, leading to a crash or potential memory corruption. The issue was identified in version 3.02:rc5.

Affected products

  • NASM Netwide Assembler (NASM) 3.02:rc5

Timeline

  • 2026-03-29: disclosed: Issue reported on NASM GitHub repository
  • 2026-04-10: advisory: CVE published by CERT/CC
  • 2026-04-16: other: NIST initial analysis completed

References

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