CVE-2026-27203
eBay API MCP Server Affected by Environment Variable Injection
Description
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. ### Impact An attacker can inject arbitrary environment variables into the `.env` file. This could lead to: - **Configuration Overwrites**: Attackers can overwrite critical settings like `EBAY_REDIRECT_URI` to hijack OAuth flows. - **Denial of Service**: Injecting invalid configuration can prevent the server from starting. - **Potential RCE**: In some environments, controlling environment variables (like `NODE_OPTIONS`) can lead to Remote Code Execution. Found with [MCPwner](https://github.com/Pigyon/MCPwner) 🕶
How to fix CVE-2026-27203
No fixed version has been published yet. Mitigate by removing the affected package or applying upstream guidance from the references below.
- —no fix listed
Is CVE-2026-27203 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, <= 1.7.2
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH8.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H |