CVE-2026-77246: mcp-atlassian Local File Exfiltration via Unvalidated Attachment Upload Path
Summary
CVE-2026-77246: MCP Atlassian: MCP HTTP Client Server-Local File Exfiltration via Unvalidated Attachment Upload Path. Affects mcp-atlassian versions < 0.22.0. Fixed in 0.22.0. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
The mcp-atlassian package is an MCP tool designed for integration with Atlassian products like Confluence and Jira. It facilitates various functionalities, including file uploads and management. However, it has a critical vulnerability that allows unauthorized file access due to improper validation of file paths during attachment uploads.
Vulnerability Detail
The vulnerability arises from the mcp-atlassian server's handling of attachment uploads, specifically through the confluence_upload_attachment tool. It allows a remote, unauthenticated attacker to exploit unvalidated file paths, potentially exfiltrating sensitive files from the server's filesystem. The attacker can manipulate HTTP headers to redirect uploads to their controlled endpoint and specify arbitrary file paths, leading to unauthorized access to files such as environment variables, SSH keys, and other sensitive data. The lack of proper path validation and authentication checks makes this vulnerability particularly severe, with a CVSS score of 7.4.
How To Fix
Latest published version: 0.23.1 as of 23 Oct 2026
pip install --upgrade "mcp-atlassian==0.23.1"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.22.0
This is the first release that contains the fix.
pip install --upgrade "mcp-atlassian==0.22.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, you can set the environment variable READ_ONLY_MODE to true, which will disable write operations, including file uploads. This can be done by adding the following line to your environment configuration: export READ_ONLY_MODE=true.
Conclusion
CVE-2026-77246 is a significant vulnerability in the mcp-atlassian package that can lead to serious security risks due to unauthorized file access. It is crucial to update to the patched version or implement the recommended workarounds to mitigate potential threats.
See every vulnerability recorded for mcp-atlassian →
FAQ
CVE-2026-77246 is a vulnerability in the mcp-atlassian package that allows for local file exfiltration through unvalidated attachment uploads.
You can check if your application is affected by using the Vulert playground at Vulert Scanner, which monitors open-source vulnerabilities in real-time.
The vulnerability can lead to unauthorized access to sensitive files on the server, including environment variables, SSH keys, and other confidential information.
Yes, a patch is available in version 0.22.0 of the mcp-atlassian package. It is recommended to update to this version or later.
If immediate updating is not possible, consider setting READ_ONLY_MODE to true to disable write operations as a temporary workaround.
References
Related vulnerabilities
Recent vulnerabilities recorded for mcp-atlassian.
