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CVE-2026-77254 – Unauthenticated Access to Jira/Confluence Data via MCP – mcp-atlassian < 0.22.0

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Summary

CVE-2026-77254 is a missing-authentication vulnerability (CWE-306) in mcp-atlassian, the open-source Model Context Protocol (MCP) server that lets AI assistants and agents interact with Jira and Confluence. When mcp-atlassian is deployed with HTTP transport and globally configured Atlassian credentials, requests to the MCP endpoint that carry no per-user identity are still allowed to reach tool handlers, which then execute using the operator’s globally configured Jira/Confluence credentials. The issue carries a CVSS v3.1 score of 9.1 (Critical) and affects all versions prior to 0.22.0.

Technical details

  • Root cause: The HTTP MCP endpoint’s authentication middleware permits requests that lack an Authorization header to pass through to tool handlers. When no per-user identity is provided, the tool-handler/fetcher construction falls back to the server’s globally configured Jira and/or Confluence credentials instead of rejecting the request.
  • Trigger conditions: The server must be run with HTTP transport and configured with global (operator-level) Jira/Confluence credentials — a documented and common pattern for multi-user/remote deployments. The default HTTP listener binds to all interfaces (0.0.0.0), increasing real-world exposure when the service is reachable over a network.
  • Attack vector: Network (AV:N), no privileges or user interaction required. An attacker who can reach the exposed MCP HTTP endpoint simply sends a POST request without an Authorization header.
  • Impact: A remote, unauthenticated network client can invoke Jira and Confluence tools with the permissions of the globally configured service account, resulting in unauthorized read and write access (high confidentiality and integrity impact) to Jira issues and Confluence content. Availability is not impacted.

Affected software

  • sooperset/mcp-atlassian, all versions prior to 0.22.0 (when deployed with HTTP transport and global Atlassian credentials configured)

Severity

  • CVSS v3.1 Base Score: 9.1 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Mitigation and recommended actions

  • Immediate: Upgrade mcp-atlassian to version 0.22.0 or later, which fixes the authentication bypass (GitHub commit b041733, PR #1448).
  • If immediate patching is not possible:
    • Do not bind the HTTP MCP server to all interfaces (0.0.0.0); restrict it to localhost or a private/internal interface.
    • Place the MCP HTTP endpoint behind an authenticating reverse proxy or API gateway that enforces per-user credentials before requests reach the server.
    • Avoid using globally configured (shared/operator-level) Jira/Confluence credentials for HTTP-transport deployments; prefer per-user OAuth/token configurations where supported.
    • Restrict network reachability of the MCP endpoint via firewall rules/network segmentation to trusted hosts only.

References

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