# CVE-2026-56787: RTKLIB 2.4.3 - Off-by-One Out-of-Bounds Read in decode_ssr3 via RTCM3 SSR Message

> Remote attackers can cause denial of service in RTKLIB rovers and CORS servers by sending crafted RTCM3 SSR messages that trigger an out-of-bounds read.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Jun 2026
- **Updated:** 14 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-56787, GHSA-8p7j-vhgr-rcw5, UBUNTU-CVE-2026-56787

## What is CVE-2026-56787?

CVE-2026-56787 is a medium-severity memory corruption vulnerability in tomojitakasu RTKLIB, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

RTKLIB through 2.4.3 contains an off-by-one out-of-bounds read vulnerability in the decode_ssr3 function at src/rtcm3.c:1446 that allows remote attackers to trigger a global buffer overflow via crafted RTCM3 SSR messages with attacker-controlled signal mode fields. Remote attackers can exploit this vulnerability by sending malicious SSR correction streams over NTRIP or serial connections to cause denial of service or crash RTKLIB rovers and CORS servers.

Weakness: CWE-193 (Off-by-one Error)

## Which versions are affected by CVE-2026-56787?

It affects 1 product.


Products: Rtklib Rtklib.

## How do I fix CVE-2026-56787?

No fix has been published for CVE-2026-56787 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-56787 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56787 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-2026-56789](https://insights.sbomify.com/CVE-2026-56789/): RTKLIB 2.4.3 - Heap Buffer Overflow and Stack Read via Oversized RINEX Epoch Satellite Count (high 7.1)
- [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-2026-56787 and fix it if it is affected.

What it is: CVE-2026-56787 is a medium-severity memory corruption vulnerability in tomojitakasu RTKLIB, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56787 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-2026-56787/ (Markdown: https://insights.sbomify.com/CVE-2026-56787/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56787
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56787
- OSV: https://osv.dev/vulnerability/CVE-2026-56787

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-56787/
Summaries are generated and may contain mistakes; the official description above is the record.