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[ CVE-2026-77244 · Published 22 Sep 2026 ]

[mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token

CVSS 10.0 EPSS <1%Fix available

[ Why it matters ]Priority signals

  • Critical severity: CVSS 10.0

[ Description ]Official description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the HTTP transport accepts requests without a verified user identity and downstream fetcher construction falls back to the operator's globally configured Jira or Confluence credentials. A network client that can reach the MCP endpoint can invoke Atlassian tools as the operator, including read and write operations available to that account. The advisory traces the vulnerable input and processing flow through UserTokenMiddleware, AtlassianOpaqueTokenVerifier, _get_fetcher, and streamable-http, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

[ Fixes ]Fixes and patches

  • mcp-atlassian 0.22.0Fixed version · GitHub Advisories · pip package mcp-atlassian: upgrade to 0.22.0 or later (affected < 0.22.0)

[ Packages ]Affected open-source packages

[ References ]References