# CVE-2026-27203: eBay API MCP Server Affected by Environment Variable Injection

> Attackers can inject arbitrary environment variables via the token update tool, potentially leading to remote code execution or denial of service.

- **Severity:** High 8.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Feb 2026
- **Updated:** 25 Feb 2026
- **Also known as:** GHSA-97rm-xj73-33jh

## What is CVE-2026-27203?

CVE-2026-27203 is a high-severity code injection vulnerability in YosefHayim ebay-mcp, published on 20 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), CWE-15 (External Control of System or Configuration Setting)

## Which versions are affected by CVE-2026-27203?

2 open source packages ship an affected version, including ebay-mcp.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ebay-mcp` | npm | All versions to 1.7.2 | None |
| `ebay-mcp` | npm | All versions to 1.7.2 | None |

## How do I fix CVE-2026-27203?

No fix has been published for CVE-2026-27203 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-27203 being exploited?

There is no known exploitation of CVE-2026-27203 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27203 and fix it if it is affected.

What it is: CVE-2026-27203 is a high-severity code injection vulnerability in YosefHayim ebay-mcp, published on 20 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-27203 in the wild and no public exploit code.

Affected packages and fixed versions:
- ebay-mcp (npm): affected all versions up to 1.7.2; no fix listed
- ebay-mcp (npm): affected all versions up to 1.7.2; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27203/ (Markdown: https://insights.sbomify.com/CVE-2026-27203/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27203
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27203
- OSV: https://osv.dev/vulnerability/CVE-2026-27203

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27203/
Summaries are generated and may contain mistakes; the official description above is the record.