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[ CVE-2026-77255 · Published 22 Sep 2026 ]

MCP Atlassian: Arbitrary File Read & Exfiltration (Confused Deputy) in JIRA update_issue

CVSS 8.6 EPSS <1%Fix available

[ Why it matters ]Priority signals

  • Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the Jira update_issue attachments argument is converted into local paths and routed to the attachment upload implementation without workspace validation. A caller can make the MCP server read arbitrary local files and attach them to a Jira issue, using the server as a confused deputy to exfiltrate the contents. The advisory traces the vulnerable input and processing flow through jira update_issue, attachments, upload_attachment, and file_path, 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