CVE-2026-55552 is a high-severity (CVSS 7.5) Path Traversal vulnerability in org.yamcs:yamcs-core. A fix is available for org.yamcs:yamcs-core — see the affected versions and patch details below.
Yamcs: Unauthenticated Directory Traversal
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55552.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-55552 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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 | 5.12.0org.yamcs:yamcs-core: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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
How to detect CVE-2026-55552
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2026-55552 -u https://target- Template
- Yamcs <=5.11.12 - Arbitrary File Read
- Severity
- high
- Impact
- Unauthenticated attackers can read arbitrary files from the host running Yamcs, including the shadow password file and the installation secret key stored in yamcs.yaml, potentially leading to full compromise of the mission control system.
- Remediation
- Update to version 5.11.13, or 5.12.0 or later, which constrain resolved static file paths to the configured static roots.
Template by ProjectDiscovery nuclei-templates (aryu-ru, AbdrrahimDahmani), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2026-55552 in your dependencies?
Find it across Maven, including transitive dependencies.