# CVE-2026-6067: NASM heap buffer overflow in obj_directive

Source: https://junglewise.ai/threats/cve-2026-6067-nasm-heap-buffer-overflow-in-obj-directive  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-10. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2026-6067 · Severity: medium · CVSS 5.5 · Published 2026-04-10

The Netwide Assembler (NASM) is a popular tool used by developers to convert assembly language code into machine-readable formats. A security flaw in this tool allows a specially crafted assembly file to crash the application or potentially allow unauthorized code execution when a user attempts to process it. This could disrupt development workflows or be used as a stepping stone for further attacks on a developer's workstation.

Technologies: [Nasm Netwide Assembler](https://junglewise.ai/threats/technologies/netwide-assembler). Vendors: [Nasm](https://junglewise.ai/threats/vendors/nasm).

## Quick answers

**Is CVE-2026-6067 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-6067 being exploited in the wild.

**How severe is CVE-2026-6067?** Medium severity, with a CVSS score of 5.5, published 10 April 2026.

**Which products and versions are affected?** NASM Project Netwide Assembler (NASM) 3.02 rc5.

**Is there a fix for CVE-2026-6067?** 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-2026-6067 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-6067?** 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 heap-based buffer overflow (CWE-787) exists in NASM within the 'obj_directive()' function located in 'output/outobj.c'. The root cause is a lack of proper bounds checking when processing the 'GROUP' directive. An attacker can exploit this by providing a malicious '.asm' source file for assembly. Successful exploitation requires a user to run NASM on the malicious file, which can lead to out-of-bounds memory writes, resulting in application crashes (DoS) or potential arbitrary code execution. The vulnerability was identified in version 3.02 rc5.

## Affected products

- NASM Project Netwide Assembler (NASM) 3.02 rc5

## Timeline

- 2026-02-27: other: Issue reported on GitHub
- 2026-04-10: disclosed: CVE published
- 2026-04-23: advisory: NVD analysis updated

## References

- [https://github.com/netwide-assembler/nasm/issues/203](https://github.com/netwide-assembler/nasm/issues/203)

## Related threats

- [NASM stack buffer overflow in disasm function](https://junglewise.ai/threats/cve-2026-6069-nasm-stack-buffer-overflow-in-disasm-function)
- [NASM heap use after free in response file processing](https://junglewise.ai/threats/cve-2026-6068-nasm-heap-use-after-free-in-response-file-processing)