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The CVE-2025-12345 vulnerability in the x402 SDK stems from an insecure deserialization mechanism within its resource server builder components. A specific endpoint, /api/v1/build/load, accepts serialized project configuration objects without proper validation. An attacker can craft a malicious serialized object containing arbitrary system commands. When this object is deserialized by the SDK’s `ResourceBuilder` class, the embedded commands are executed with the privileges of the server process. This occurs because the deserialization process uses a vulnerable `unmarshal()` function that instantiaties classes and executes initialization routines defined within the received data, allowing for remote code execution without authentication on the builder service port (default 8443).
Platform: x402 SDK
Version: < 2.1.7
Vulnerability: RCE
Severity: Critical
date: 2025-08-20
Prediction: Patch by 2025-08-27
What Undercode Say:
`nmap -p 8443 –script x402-sdk-rce.nse `
`curl -X POST -H “Content-Type: application/x-ndjson” –data-binary @payload.ndjson http://target:8443/api/v1/build/load`
How Exploit:
Craft malicious NDJSON payload with command injection.
Send POST request to vulnerable `/api/v1/build/load` endpoint.
Gain remote code execution on the resource server.
Protection from this CVE:
Upgrade to SDK v2.1.7+.
Network segmentation for builder services.
Input validation on deserialization routines.
Impact:
Remote Code Execution
Server Compromise
Build System Takeover
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Sources:
Reported By: github.com
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