CVE-2026-27203
HIGH
GHSA-97rm-xj73-33jh
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
Lifecycle Timeline
2Tags
Description
eBay API MCP Server is an open source local MCP server providing AI assistants with comprehensive access to eBay's Sell APIs. All versions are vulnerable to Environment Variable Injection through the updateEnvFile function. The ebay_set_user_tokens tool allows updating the .env file with new tokens. The updateEnvFile function in src/auth/oauth.ts blindly appends or replaces values without validating them for newlines or quotes. This allows an attacker to inject arbitrary environment variables into the configuration file. An attacker can inject arbitrary environment variables into the .env file. This could lead to configuration overwrites, Denial of Service, and potential RCE. There was no fix for this issue at the time of publication.
Analysis
eBay API MCP Server's ebay_set_user_tokens tool fails to validate environment variable inputs in the updateEnvFile function, allowing authenticated attackers to inject arbitrary variables into the .env configuration file. An attacker with login credentials can exploit this to overwrite existing configurations, trigger denial of service conditions, or achieve remote code execution through malicious environment variable injection. …
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Remediation
Within 24 hours: Identify all systems running eBay API MCP Server and isolate them from production networks if possible; notify relevant business stakeholders. Within 7 days: Implement network segmentation to restrict API server access, disable the updateEnvFile function if not critical to operations, and audit recent environment variable changes for signs of compromise. …
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