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

> Attackers can execute arbitrary code or crash applications by providing malicious RINEX files with excessive satellite counts to RTKLIB.

- **Severity:** High 7.1 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 25 Jun 2026
- **Updated:** 14 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-56789, GHSA-3fqf-8h5x-pq8x, UBUNTU-CVE-2026-56789

## What is CVE-2026-56789?

CVE-2026-56789 is a high-severity memory corruption vulnerability in tomojitakasu RTKLIB, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-56789?

It affects 1 product.


Products: Rtklib Rtklib.

## How do I fix CVE-2026-56789?

No fix has been published for CVE-2026-56789 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-56789 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56789 exists.

## Other vulnerabilities in tomojitakasu RTKLIB

- [CVE-2026-56786](https://insights.sbomify.com/CVE-2026-56786/): RTKLIB 2.4.3 - Out-of-bounds Write in decode_type1033 via Crafted RTCM3 Message (critical 9.3)
- [CVE-2026-56787](https://insights.sbomify.com/CVE-2026-56787/): RTKLIB 2.4.3 - Off-by-One Out-of-Bounds Read in decode_ssr3 via RTCM3 SSR Message (medium 6.9)
- [CVE-2026-56788](https://insights.sbomify.com/CVE-2026-56788/): RTKLIB 2.4.3 - Out-of-bounds Read via Negative Array Index in getcodepri (medium 4.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56789 and fix it if it is affected.

What it is: CVE-2026-56789 is a high-severity memory corruption vulnerability in tomojitakasu RTKLIB, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56789 exists.

Affected product: tomojitakasu RTKLIB. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-56789/ (Markdown: https://insights.sbomify.com/CVE-2026-56789/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56789
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56789
- OSV: https://osv.dev/vulnerability/CVE-2026-56789

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-56789/
Summaries are generated and may contain mistakes; the official description above is the record.