# CVE-2026-56789: RTKLIB heap buffer overflow in readrnxobsb function

Source: https://junglewise.ai/threats/cve-2026-56789-rtklib-heap-buffer-overflow-in-readrnxobsb-function  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-25. Updated: 2026-06-25  
License: CC BY 4.0 with a link back

CVE-2026-56789 · Severity: medium · CVSS 6.5 · Published 2026-06-25

RTKLIB is an open-source program package for standard and precise positioning with GNSS (Global Navigation Satellite System). A vulnerability in how it processes satellite data files could allow an attacker to crash applications using this library, such as rnx2rtkp and RTKPOST, by providing a specially crafted file. This could lead to a denial of service, interrupting precise positioning and navigation operations.

Technologies: [Tomoji Takasu RTKLIB](https://junglewise.ai/threats/technologies/rtklib). Vendors: [Tomoji Takasu](https://junglewise.ai/threats/vendors/tomoji-takasu).

## Quick answers

**Is CVE-2026-56789 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-56789 being exploited in the wild.

**How severe is CVE-2026-56789?** Medium severity, with a CVSS score of 6.5, published 25 June 2026.

**Which products and versions are affected?** Tomoji Takasu RTKLIB through 2.4.3.

**Is there a fix for CVE-2026-56789?** 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-2026-56789 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-56789?** Check whether you run Tomoji Takasu RTKLIB 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 heap-based buffer overflow exists in RTKLIB versions up to and including 2.4.3 within the readrnxobsb function in src/rinex.c. The vulnerability is caused by a failure to properly validate or 'clamp' the satellite count values provided in RINEX epoch headers. By crafting a RINEX file that declares more than 64 satellites per epoch, an attacker can trigger heap buffer overflow writes and out-of-bounds stack reads. This typically results in a crash (Denial of Service) of applications linked against the library, such as rnx2rtkp and RTKPOST. Exploitation requires the victim to open or process a malicious RINEX file.

## Affected products

- tomojitakasu RTKLIB through 2.4.3

## Timeline

- 2026-06-25: disclosed
- 2026-06-25: advisory

## References

- [https://github.com/tomojitakasu/RTKLIB/issues/796](https://github.com/tomojitakasu/RTKLIB/issues/796)
- [https://www.vulncheck.com/advisories/rtklib-heap-buffer-overflow-and-stack-read-via-oversized-rinex-epoch-satellite-count](https://www.vulncheck.com/advisories/rtklib-heap-buffer-overflow-and-stack-read-via-oversized-rinex-epoch-satellite-count)

## Related threats

- [RTKLIB out-of-bounds read in getcodepri function](https://junglewise.ai/threats/cve-2026-56788-rtklib-out-of-bounds-read-in-getcodepri-function)
- [RTKLIB off-by-one error in decode_ssr3 function](https://junglewise.ai/threats/cve-2026-56787-rtklib-off-by-one-error-in-decode-ssr3-function)
- [RTKLIB out-of-bounds write in decode_type1033](https://junglewise.ai/threats/cve-2026-56786-rtklib-out-of-bounds-write-in-decode-type1033)