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eBay API MCP Server Affected by Environment Variable Injection

High severity GitHub Reviewed Published Feb 18, 2026 in YosefHayim/ebay-mcp • Updated Feb 23, 2026

Package

npm ebay-mcp (npm)

Affected versions

<= 1.7.2

Patched versions

None

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 🕶

References

@YosefHayim YosefHayim published to YosefHayim/ebay-mcp Feb 18, 2026
Published to the GitHub Advisory Database Feb 19, 2026
Reviewed Feb 19, 2026
Published by the National Vulnerability Database Feb 21, 2026
Last updated Feb 23, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(4th percentile)

Weaknesses

External Control of System or Configuration Setting

One or more system settings or configuration elements can be externally controlled by a user. Learn more on MITRE.

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. Learn more on MITRE.

CVE ID

CVE-2026-27203

GHSA ID

GHSA-97rm-xj73-33jh

Source code

Credits

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