# CVE-2026-54417: rxi microtar integer overflow in mtar_next

Source: https://junglewise.ai/threats/cve-2026-54417-rxi-microtar-integer-overflow-in-mtar-next  
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-2026-54417 · Severity: high · CVSS 7.5 · Published 2026-06-17

rxi microtar is a lightweight C library used for reading and writing tar archives. A flaw in how the library calculates file positions allows a specially crafted archive to trigger an infinite loop. This can cause applications using the library to hang and consume 100% of the CPU, leading to a total denial of service.

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

## Quick answers

**Is CVE-2026-54417 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-54417 being exploited in the wild.

**How severe is CVE-2026-54417?** High severity, with a CVSS score of 7.5, published 17 June 2026.

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

**Is there a fix for CVE-2026-54417?** 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-2026-54417 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-54417?** 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

An integer overflow exists in the mtar_next() function within src/microtar.c of rxi microtar 0.1.0. The function calculates the offset to the next record using 32-bit arithmetic: round_up(h.size, 512) + sizeof(mtar_raw_header_t). If a crafted tar header specifies a size that, when rounded and added to the header size, results in a 32-bit integer wrap-around to zero (specifically sizes in the range 0xFFFFFC01-0xFFFFFE00), the library seeks to the current record position instead of advancing. This causes mtar_find() or any iteration loop to repeat indefinitely, resulting in 100% CPU consumption and a process hang. The vulnerability can be triggered by any application that parses untrusted tar files using this library.

## Affected products

- rxi microtar 0.1.0

## Timeline

- 2026-06-17: advisory: NVD publication date

## 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 stack buffer overflow in raw_to_header](https://junglewise.ai/threats/cve-2026-55738-rxi-microtar-stack-buffer-overflow-in-raw-to-header)
- [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)