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VulnerabilityPublished Updated

CVE-2026-27203: YosefHayim ebay-mcp · External Control of System or Configuration Setting

Affects YosefHayim ebay-mcpSource CVE Database V5

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Not known to be exploited · CVSS 8.3 High.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score
8.3High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Feb 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
YosefHayimebay-mcpAffected
  • <=1.7.2
Fixed in–

AI-suggested

To mitigate CVE-2026-27203, organizations should immediately restrict access to the ebay_set_user_tokens tool and the updateEnvFile function to trusted administrators only, minimizing the risk of unauthorized environment variable injection. Implement strict input validation and sanitization routines to reject any input containing newline characters, quotes, or other special characters that could enable injection attacks. Employ file integrity monitoring on the .env configuration file to detect unauthorized changes promptly. Consider isolating the MCP server in a segmented network zone with limited exposure to untrusted networks. Until an official patch is released, evaluate the feasibility of applying custom patches that enforce input validation or temporarily disable the vulnerable update functionality. Regularly audit logs for suspicious activity related to environment variable updates. Finally, maintain up-to-date backups of configuration files to enable rapid recovery in case of corruption or compromise.

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.

References

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