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Vulnerability · Published Sep 22, 2026 · Assigned by GitHub_M

CVE-2026-77248MCP Atlassian: Unauthenticated arbitrary local file read via upload_attachment file_path, chained with missing auth on streamable-http transport

High 8.6

In plain English

A high-severity path traversal in mcp-atlassian from sooperset. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.6High
Exploit odds (30 days)0.5%top 58.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the streamable HTTP transport accepts requests without a user identity and falls back to operator credentials, while upload_attachment accepts an unrestricted file_path. An unauthenticated network caller can read files available to the MCP process, upload them to an attacker-selected Jira issue or Confluence page, and retrieve the contents. The advisory traces the vulnerable input and processing flow through streamable-http, UserTokenMiddleware, upload_attachment, file_path, and _get_fetcher, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPImcp-atlassian0.22.0GHSA-cc5h-2pwp-pvcc
PyPImcp-atlassian0.22.0PYSEC-2026-4089

Affected products (as reported)

VendorProductVersions
sooperset mcp-atlassian < 0.22.0

Weakness: CWE-22, CWE-306 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

References