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CVE-2025-55182 is a severe pre-authentication remote code execution vulnerability impacting React Server Components within versions 19.0 through 19.2.0.
The vulnerability arises because the server-side runtime processes untrusted client data without proper validation or sanitization during deserialization.
Specifically, when handling serialized payloads via the Flight protocol, React traverses chunks to resolve object references.
In vulnerable versions, the traversal mechanism fails to verify whether a requested key is explicitly set on the object.
This flaw allows an unauthenticated attacker to traverse properties and access the underlying JavaScript object prototype.
By crafting a malicious payload where an object chunk sets its reference key to the built-in function constructor, the application evaluates untrusted code.
When Next.js or other RSC-based frameworks parse the model string using functions like decodeReplyFromBusboy, they await the returned thenable chunk.
V8 evaluates this awaited function, triggering the serialized code execution context seamlessly.
Because React’s runtime architecture was never originally engineered to safely ingest direct untrusted client input payloads, this oversight permits full remote server compromise.
Attackers can exploit this vulnerability using a single, unauthenticated crafted HTTP request sent directly to any active Server Function endpoint.
The flaw bypasses traditional security boundaries, facilitating unauthorized persistence, backdoor deployment, and data exfiltration.
Organizations running affected versions face widespread exposure unless immediate upgrades or mitigations are applied.
The issue affects multiple ecosystem packages including react-server-dom-webpack, react-server-dom-turbopack, and react-server-dom-parcel.
Security teams have tracked active exploitation in the wild, adding the vulnerability to CISA’s Known Exploited Vulnerabilities catalog.
Remediation requires updating affected packages to patched versions released by the React team.
DailyCVE Form:
Platform: React Server Components
Version: 19.0 through 19.2
Vulnerability: Remote code execution
Severity: Critical score ten
date: December 3 2025
Prediction: December 2025 patch
What Undercode Say:
To analyze and verify vulnerability handling in your environment, you can check installed package versions and inspect network traffic using standard bash commands.
Run the following command to find vulnerable React packages in your Node modules:
`npm list react react-server-dom-webpack`
To monitor incoming HTTP payloads for suspicious serialized function patterns, execute this tcpdump filter:
`tcpdump -nnvvA -s0 ‘tcp port 3000 and (((ip[2:2] – ((ip[bash]&0xf)<<2)) - ((tcp[bash]&0xf0)>>2)) != 0)’ | grep -i “__proto__”`
Always ensure your dependencies are locked and audited against known advisory lists.
Exploit: (Educational Purposes!)
An attacker crafts a malicious HTTP POST request targeting a Server Function endpoint with a serialized payload designed to target prototype properties.
The payload references chunk structures where missing key validation exposes the Function constructor via object prototype chaining.
When the server deserializes the payload, the framework awaits the crafted thenable object returned by the parsing routine.
The JavaScript engine executes the constructor function context, leading to arbitrary command execution on the host server.
No user interaction or prior authentication is required to trigger this execution chain.
Protection: from this CVE
Upgrade all affected React Server Components packages to the latest patched versions provided by the official vendor advisory.
Implement strict input validation and boundary checks at the web application firewall level to block anomalous serialized payloads containing prototype references.
Monitor server processes and container environments using endpoint detection tools for unexpected spawned child processes or reverse shell activity.
Impact:
Successful exploitation grants an unauthenticated attacker full remote code execution capabilities leading to complete server takeover.
Threat actors can deploy backdoors, harvest cloud credentials, execute cryptomining scripts, and compromise underlying infrastructure integrity.
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Sources:
Reported By: github.com
Extra Source Hub:
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