Detect Prototype Pollution in @deepstream/server (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 within the Node.js server process.
MITRE ATT&CK
YARA-L Detection Query
rule cve_2026_49252_deepstream_prototype_pollution {
meta:
author = "df00tech Detection Platform"
description = "Detects prototype pollution exploitation attempts against @deepstream/server (CVE-2026-49252)"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://github.com/advisories/GHSA-9v98-6g37-x9g6"
events:
(
$e.metadata.event_type = "PROCESS_LAUNCH"
AND (
$e.target.process.command_line = /deepstream/ nocase
OR $e.principal.process.command_line = /deepstream/ nocase
)
) OR (
$e.metadata.event_type = "NETWORK_CONNECTION"
AND $e.target.port = 6020
)
AND (
$e.target.process.command_line = /__proto__/ nocase
OR $e.target.process.command_line = /constructor/ nocase
)
condition:
$e
}Chronicle YARA-L rule detecting deepstream process launches or network connections on default deepstream ports combined with prototype pollution payload indicators in command line arguments.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate deepstream server management commands that reference constructor in benign contexts
- Security scanning integrations that probe deepstream endpoints as part of authorized assessments
- CI/CD pipelines running integration tests against deepstream that exercise prototype-related test cases
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 Client Message
Expected signal: Node.js application logs should show receipt of a record set message with __proto__ key; process monitoring may show unexpected property on Object.prototype after message processing
- Test 2deepstream Server Version Enumeration
Expected signal: Process execution event for node reading package.json; stdout output containing version string below 10.0.5 confirms vulnerability
- Test 3Prototype Pollution Object Property Verification
Expected signal: Node.js process execution with inline script; stdout output 'YES - VULNERABLE' confirms Object.prototype susceptibility
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