CVE-2026-77246

MCP Atlassian: MCP HTTP Client Server-Local File Exfiltration via Unvalidated Attachment Upload Path

State: Published
Severity: 7.4 High
Published: Sep 22, 2026
Updated: Sep 24, 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, an HTTP transport deployment with READ_ONLY_MODE=false accepts a request without an Authorization identity and permits attacker-controlled Atlassian service headers, including X-Atlassian-Confluence-Url, to select a public attacker hostname or one allowed by MCP_ALLOWED_URL_DOMAINS. A caller can then invoke confluence_upload_attachment or the Jira attachment variant in src/mcp_atlassian/jira/attachments.py with a server-local file_path and cause the MCP process to send the file to the selected attachment endpoint. This issue is fixed in version 0.22.0.

Scores

CVSS	Score	Vector	Source
3.1	7.4 High	CVSS:3.1/AV:A/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-200 Exposure of Sensitive Information to an Unauthorized Actor
CWE-441 Unintended Proxy or Intermediary ('Confused Deputy')

Affected Products

Product	Versions
mcp-atlassiansooperset	< 0.22.0Affected

References

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