# [CRIT] [GHSA / CRITICAL] CVE-2026-44632: Yamcs Vulnerable to Server-Side Code Injection (RCE) via Janino Expression Engine in `JavaExprAlgorithmExecutionFactory`

**Source:** GitHub Security Advisories
**Published:** 2026-05-27
**Article:** https://github.com/advisories/GHSA-524g-x36v-9wm6

## Threat Profile

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

### 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 Remo…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2026-44632`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1021.002** — SMB/Windows Admin Shares
- **T1569.002** — Service Execution
- **T1219** — Remote Access Software
- **T1204.002** — User Execution: Malicious File
- **T1059.004** — Command and Scripting Interpreter: Unix Shell
- **T1059** — Command and Scripting Interpreter
- **T1071.001** — Application Layer Protocol: Web Protocols
- **T1041** — Exfiltration Over C2 Channel
- **T1082** — System Information Discovery

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Yamcs JVM spawning OS shell/interpreter (Janino RCE via CVE-2026-44632)

`UC_202_4` · phase: **exploit** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.parent_process_name IN ("java","java.exe","yamcsd","yamcs")) (Processes.process_name IN ("bash","sh","dash","zsh","curl","wget","python","python3","nc","ncat","cmd.exe","powershell.exe")) by Processes.dest Processes.user Processes.parent_process Processes.process Processes.process_name Processes.parent_process_name | `drop_dm_object_name(Processes)` | convert ctime(firstTime) ctime(lastTime) | sort - lastTime
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where InitiatingProcessFileName in~ ("java","java.exe","yamcsd","yamcs")
| where FileName in~ ("bash","sh","dash","zsh","curl","wget","python","python3","nc","ncat","cmd.exe","powershell.exe")
| where AccountName !endswith "$"
| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessCommandLine, FileName, ProcessCommandLine, SHA256
| order by Timestamp desc
```

### Yamcs MDB algorithm override PATCH with Java Runtime payload

`UC_202_5` · phase: **delivery** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Web.Web where (Web.http_method="PATCH") (Web.url="*/api/mdb/*/algorithms/*") by Web.src Web.dest Web.url Web.http_method Web.user Web.http_user_agent | `drop_dm_object_name(Web)` | convert ctime(firstTime) ctime(lastTime) | sort - lastTime
```

### Outbound recon callback from Yamcs host (curl/shell child of JVM to public IP)

`UC_202_6` · phase: **c2** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic.All_Traffic where (All_Traffic.app IN ("curl","wget","bash","sh","python","python3","nc","ncat")) (All_Traffic.direction="outbound" OR All_Traffic.dest_category="external") by All_Traffic.src All_Traffic.dest All_Traffic.dest_port All_Traffic.app | `drop_dm_object_name(All_Traffic)` | convert ctime(firstTime) ctime(lastTime) | sort - lastTime
```

**Defender KQL:**
```kql
DeviceNetworkEvents
| where Timestamp > ago(7d)
| where InitiatingProcessParentFileName in~ ("java","java.exe","yamcsd","yamcs")
| where InitiatingProcessFileName in~ ("curl","wget","bash","sh","python","python3","nc","ncat")
| where RemoteIPType == "Public"
| project Timestamp, DeviceName, InitiatingProcessAccountName, InitiatingProcessParentFileName, InitiatingProcessFileName, InitiatingProcessCommandLine, RemoteIP, RemoteUrl, RemotePort
| order by Timestamp desc
```

### Remote service execution — PsExec / SMB lateral movement

`UC_LATERAL_PSEXEC` · phase: **actions** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.process_name IN ("psexec.exe","psexesvc.exe","paexec.exe","smbexec.py")
       OR (Processes.process_name="wmic.exe" AND Processes.process="*/node:*")
    by Processes.dest, Processes.user, Processes.process_name, Processes.process, Processes.parent_process_name
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where FileName in~ ("psexec.exe","psexesvc.exe","paexec.exe","smbexec.py")
   or (FileName =~ "wmic.exe" and ProcessCommandLine has "/node:")
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine, InitiatingProcessFileName
| order by Timestamp desc
```

### RMM tool installed by non-IT user — remote-access utility for hands-on-keyboard

`UC_RMM_TOOLS` · phase: **install** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.process_name IN ("AnyDesk.exe","TeamViewer.exe","TeamViewer_Service.exe",
        "ScreenConnect.ClientService.exe","ConnectWiseControl.ClientService.exe",
        "atera_agent.exe","SplashtopStreamer.exe","RustDesk.exe","NinjaOne.exe","kaseya*.exe")
    by Processes.dest, Processes.user, Processes.process_name, Processes.process, Processes.parent_process_name
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where FileName in~ ("AnyDesk.exe","TeamViewer.exe","TeamViewer_Service.exe",
        "ScreenConnect.ClientService.exe","ConnectWiseControl.ClientService.exe",
        "atera_agent.exe","SplashtopStreamer.exe","RustDesk.exe","NinjaOne.exe")
   or FileName matches regex @"(?i)kaseya.*\.exe"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine
```

### Article-specific behavioural hunt — [GHSA / CRITICAL] CVE-2026-44632: Yamcs Vulnerable to Server-Side Code Injection

`UC_202_3` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-44632: Yamcs Vulnerable to Server-Side Code Injection ```
| tstats `summariesonly` count earliest(_time) AS firstTime latest(_time) AS lastTime
    from datamodel=Endpoint.Processes
    where (Processes.process_name IN ("simulator.py"))
    by Processes.dest, Processes.user, Processes.process_name,
       Processes.process, Processes.parent_process_name, Processes.process_path
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| append [
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_name IN ("simulator.py"))
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
]
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-44632: Yamcs Vulnerable to Server-Side Code Injection
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.
DeviceProcessEvents
| where Timestamp > ago(30d)
| where (FileName in~ ("simulator.py"))
| project Timestamp, DeviceName, AccountName, FileName,
          FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
| order by Timestamp desc

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FileName in~ ("simulator.py"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2026-44632`


## Why this matters

Severity classified as **CRIT** based on: CVE present, 7 use case(s) fired, 10 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.