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Vulnerability · Published Sep 22, 2026 · Assigned by GitHub_M

CVE-2026-77266MCP Atlassian: Path traversal in upload_attachment allows arbitrary file read and exfiltration via MCP tool call

Medium 6.5

In plain English

A medium-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 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.5%top 57.0% 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, upload_attachment accepts absolute paths and traversal sequences without constraining the resolved path to the server workspace. An MCP caller with attachment access can read a chosen server-local file and exfiltrate it through Jira or Confluence. The advisory traces the vulnerable input and processing flow through upload_attachment, file_path, and path traversal, 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-mfv2-4wvm-9pgp
PyPImcp-atlassian0.22.0PYSEC-2026-4097

Affected products (as reported)

VendorProductVersions
sooperset mcp-atlassian < 0.22.0

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

References