Unintended Proxy or Intermediary ('Confused Deputy') Affecting mcp-atlassian package, versions <0.23.0-r0


Severity

Recommended
0.0
medium
0
10

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Threat Intelligence

EPSS
0.31% (21st percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-MCPATLASSIAN-18015564
  • published19 Jul 2026
  • disclosed3 Apr 2026

Introduced: 3 Apr 2026

CVE-2026-27124  (opens in a new tab)
CWE-441  (opens in a new tab)

How to fix?

Upgrade Chainguard mcp-atlassian to version 0.23.0-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream mcp-atlassian package and not the mcp-atlassian package as distributed by Chainguard. See How to fix? for Chainguard relevant fixed versions and status.

FastMCP is the standard framework for building MCP applications. Prior to version 3.2.0, while testing the GitHubProvider OAuth integration, which allows authentication to a FastMCP MCP server via a FastMCP OAuthProxy using GitHub OAuth, it was discovered that the FastMCP OAuthProxy does not properly validate the user's consent upon receiving the authorization code from GitHub. In combination with GitHub’s behavior of skipping the consent page for previously authorized clients, this introduces a Confused Deputy vulnerability. This issue has been patched in version 3.2.0.

CVSS Base Scores

version 3.1