CVE-2026-44632: Yamcs Vulnerable to Server-Side Code Injection (RCE) via Janino Expression Engine in `JavaExprAlgorithmExecutionFactory`

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 1.1%, percentile 66: FIRST’s model estimates a 1.1% chance of exploitation activity in the next 30 days, higher than 66% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Needs an account (high (admin)). Exposure depends on who can log in.
• Only applies if your dependency tree includes org.yamcs:yamcs-core (Maven) < 5.12.7, fixed in 5.12.7. Check your lockfile, including transitive dependencies.

What it is

Yamcs is a mission control framework. Prior to 5.12.7, a server-side code injection vulnerability existed in the Yamcs algorithm evaluation engine org.yamcs.algorithms.JavaExprAlgorithmExecutionFactory, which dynamically compiled and evaluated user-controlled algorithm text through the Janino compiler without enforcing a secure sandbox, so an authenticated user with the ChangeMissionDatabase privilege could override an existing algorithm's text via the mission database REST API and inject Java code (for example using java.lang.Runtime) to achieve remote code execution on the underlying host operating system. This issue is fixed in versions 5.12.7 and 5.13.0, which disable algorithm editing by default.

From the GitHub advisory

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: 1. A running Yamcs instance with an active processor (e.g., instance=myproject, processor=realtime). 2. An active authentication token for a user with the SystemPrivilege.ChangeMissionDatabase privilege.

Steps to Reproduce:

1. Send an authenticated HTTP PATCH request to the MDB override endpoint to inject the malicious Java code into an existing algorithm (e.g., copySunsensor). The payload uses java.lang.Runtime to execute a reverse shell or ping an external webhook.

Weakness type: CWE-94.

Product: org.yamcs:yamcs-core (Maven) · Assigned by: GitHub_M · Published: 2026-07-16

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: high (admin)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.12% probability of exploitation activity in the next 30 days; percentile 66.

Timeline

• 2026-05-27 — GitHub-reviewed advisory GHSA-524g-x36v-9wm6 published (critical)
• 2026-07-16 — CVE record last updated
• 2026-07-16 — CVE record published by GitHub_M

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-524g-x36v-9wm6 github.com
2. CVE.org record CVE-2026-44632 cve.org
3. NVD entry CVE-2026-44632 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. github.com github.com

Critical Maven advisories · Today’s Security Digest