# CVE-2026-55738: rxi microtar stack buffer overflow in raw_to_header

Source: https://junglewise.ai/threats/cve-2026-55738-rxi-microtar-stack-buffer-overflow-in-raw-to-header  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-17. Updated: 2026-06-20  
License: CC BY 4.0 with a link back

CVE-2026-55738 · Severity: high · CVSS 8.8 · Published 2026-06-17

rxi microtar is a lightweight C library used for reading and writing TAR archive files. A security flaw in how the library handles file names within these archives allows a specially crafted file to crash an application or potentially execute unauthorized code. This occurs when a user or automated system attempts to open or process a malicious TAR archive using the library.

Technologies: [Rxi Microtar](https://junglewise.ai/threats/technologies/microtar). Vendors: [Rxi](https://junglewise.ai/threats/vendors/rxi).

## Quick answers

**Is CVE-2026-55738 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55738 being exploited in the wild.

**How severe is CVE-2026-55738?** High severity, with a CVSS score of 8.8, published 17 June 2026.

**Which products and versions are affected?** Rxi Microtar 0.1.0.

**Is there a fix for CVE-2026-55738?** 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-2026-55738 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-55738?** Check whether you run Rxi Microtar at an affected version. 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 exists in the raw_to_header() function in src/microtar.c of rxi microtar 0.1.0. The vulnerability is caused by the use of strcpy() to copy the 100-byte 'name' and 'linkname' fields from a TAR header without ensuring the source fields are null-terminated. While the POSIX ustar format allows these fields to be fully populated, microtar fails to account for this, leading to an out-of-bounds read and subsequent stack overflow when processing a crafted archive. Attackers can trigger this via mtar_open(), mtar_read_header(), or mtar_find(). As of the advisory, no official patch is mentioned, though the issue is confirmed via AddressSanitizer.

## Affected products

- rxi microtar 0.1.0

## Timeline

- 2026-06-17: disclosed: Vulnerability published to NVD

## References

- [https://github.com/rxi/microtar](https://github.com/rxi/microtar)
- [https://github.com/rxi/microtar/blob/master/src/microtar.c](https://github.com/rxi/microtar/blob/master/src/microtar.c)
- [https://raw.githubusercontent.com/rxi/microtar/master/src/microtar.c](https://raw.githubusercontent.com/rxi/microtar/master/src/microtar.c)

## Related threats

- [rxi microtar integer overflow in mtar_next](https://junglewise.ai/threats/cve-2026-54417-rxi-microtar-integer-overflow-in-mtar-next)
- [rxi microtar stack buffer overflow in raw_to_header](https://junglewise.ai/threats/cve-2026-43623-rxi-microtar-stack-buffer-overflow-in-raw-to-header)