CVE-2026-55552 is a high-severity (CVSS 7.5) Path Traversal vulnerability in org.yamcs:yamcs-core. O3 Security confirms whether CVE-2026-55552 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Yamcs has Unauthenticated Directory Traversal
Real-World Exposure
org.yamcs:yamcs-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Attack type:
Unauthenticated remote
Impact:
Attackers can access any system files from the underlying host.
Affected components: HttpRequestHandler.java, StaticFileHandler.java
An Unauthenticated Directory Traversal vulnerability exists in Yamcs <=5.8.6, allowing anyone to access any file on the underlying operating system. This allows unauthenticated attackers to download sensitive files and data.
<img width="2170" height="1289" alt="image" src="https://github.com/user-attachments/assets/8d426da1-5351-4240-a290-8d858be61312" />Steps to Reproduce:
- Start Yamcs and login as a user
- Paste the following URL in the browser and press enter:
http://localhost:8090//etc/passwd
- The
/etc/passwdfile will be downloaded.
Acknowledgements
This vulnerability was discovered by Abderrahim Dahmani while solving a STARPWN 2025 CTF challenge at DEFCON 33 offered by VisionSpace Technologies.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.yamcs:yamcs-core | all versions | 5.12.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.yamcs:yamcs-core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.yamcs:yamcs-core to 5.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55552 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-55552 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-55552. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-55552 in your dependencies?
O3 detects CVE-2026-55552 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.