Summary
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_URIto 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 🕶
CVE-2026-27203 has a CVSS score of 8.3 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-27203? CVE-2026-27203 is a high-severity security vulnerability in ebay-mcp (npm), affecting versions <= 1.7.2. No fixed version is listed yet.
- How severe is CVE-2026-27203? CVE-2026-27203 has a CVSS score of 8.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of ebay-mcp are affected by CVE-2026-27203? ebay-mcp (npm) versions <= 1.7.2 is affected.
- Is there a fix for CVE-2026-27203? No fixed version is listed for CVE-2026-27203 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-27203 exploitable, and should I be worried? Whether CVE-2026-27203 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-27203 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.