CVE-2026-77255

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

State: Published
Severity: 8.6 High
Published: Sep 22, 2026
Updated: Sep 26, 2026
Reserved: Aug 20, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	8.6 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N	GitHub_M

Weaknesses

CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-441 Unintended Proxy or Intermediary ('Confused Deputy')

Affected Products

Product	Versions
mcp-atlassiansooperset	< 0.22.0Affected

References

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