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CVE-2026-49252 is a critical prototype pollution vulnerability (CWE-1321) affecting the @deepstream/server package versions prior to 10.0.5. Prototype pollution occurs when an application improperly handles user-supplied input, allowing an attacker to inject properties into the base objects of the software’s underlying language. In the context of deepstream, a server that enables real-time data synchronization, messaging, and RPCs at scale, this flaw can be exploited by any authenticated user with write permission to any record. By manipulating object prototypes through the data synchronization mechanism, an attacker can escalate privileges and modify any record within the system. The vulnerability was assigned a CVSS score of 9.9, indicating critical severity. Exploitation is possible over the network, making it a significant threat to deployments using affected versions. The issue was fixed in version 10.0.5. GuardVibe, a security MCP server for AI-assisted development, includes detection rules for this CVE, flagging vulnerable dependency versions in package.json files. This demonstrates how supply chain security tools can alert developers to critical vulnerabilities in their dependencies, enabling timely remediation. The vulnerability was published on 2026-06-18 and affects all versions of @deepstream/server below 10.0.5. Attackers can exploit this by sending crafted payloads that pollute Object.prototype, leading to unexpected behavior and potential remote code execution in certain contexts. The deepstream server’s data synchronization feature allows clients to send messages and make RPCs, which can be abused to inject malicious properties. Once the prototype is polluted, any object created in the application may inherit the malicious properties, potentially bypassing security checks or altering application logic. This makes the vulnerability particularly dangerous in multi-tenant environments where users have varying levels of access. GuardVibe’s rule set includes a specific rule (VG1098) that detects @deepstream/server versions below 10.0.5, alerting developers during code scanning. The fix in version 10.0.5 involves proper sanitization of user input and freezing of object prototypes to prevent pollution. Organizations using deepstream should immediately upgrade to version 10.0.5 or later to mitigate this risk. Additionally, using GuardVibe’s scanning capabilities can help identify this and other vulnerabilities in the software supply chain before deployment.
DailyCVE Form:
Platform: guardvibe
Version: 3.29.0
Vulnerability: Prototype Pollution
Severity: Critical
date: 2026-06-18
Prediction: 2026-06-27
What Undercode Say:
npx guardvibe scan --rule VG1098 npx guardvibe audit --package @deepstream/server npx guardvibe doctor --cve CVE-2026-49252
{
"dependencies": {
"@deepstream/server": "10.0.4"
}
}
npm install @deepstream/[email protected]
Exploit: (Educational Purposes!)
An authenticated user with write permission to any record can send a crafted payload through the deepstream data synchronization mechanism. The payload contains a `__proto__` property that pollutes the global Object prototype. Once polluted, subsequent object creations inherit malicious properties, allowing privilege escalation and unauthorized record modification. This exploit requires network access to the deepstream server and valid credentials.
Protection: from this CVE
Upgrade @deepstream/server to version 10.0.5 or later. Implement input validation and sanitization for all user-supplied data. Freeze object prototypes using `Object.freeze(Object.prototype)` where feasible. Use GuardVibe to scan dependencies and detect vulnerable versions before deployment. Monitor for suspicious prototype manipulation attempts in application logs.
Impact:
Successful exploitation allows any authenticated user with write permission to escalate privileges and modify any record in the deepstream server. This can lead to data corruption, unauthorized access to sensitive information, and potential full system compromise. In multi-tenant environments, an attacker could cross tenant boundaries and compromise other users’ data. The critical severity rating reflects the ease of exploitation and the high impact on confidentiality, integrity, and availability.
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Sources:
Reported By: github.com
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