CVE-2026-77259: mcp-atlassian Arbitrary File Read Vulnerability via confluence_upload_attachment
Summary
CVE-2026-77259: Missing path validation in confluence_upload_attachment allows any authenticated MCP client to read arbitrary files from the server filesystem and exfiltrate their contents to Confluence. Affects mcp-atlassian versions < 0.22.0. Fixed in 0.22.0. How to fix ↓
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Background
mcp-atlassian is a Python package designed to facilitate interactions with Atlassian products, particularly Confluence and Jira. It allows users to upload attachments, manage content, and automate workflows within these platforms. However, a critical vulnerability exists in the file upload functionality, which can lead to unauthorized access to sensitive files on the server.
Vulnerability Detail
The vulnerability arises from missing path validation in the confluence_upload_attachment function, allowing authenticated clients to read arbitrary files from the server's filesystem. Specifically, the function opens a caller-supplied file path without any boundary checks. This oversight can lead to the exfiltration of sensitive data, such as server credentials, particularly on Linux systems where /proc/self/environ can be accessed to retrieve all runtime secrets in a single call. The vulnerability is classified as high severity with a CVSS score of 7.7, indicating a significant risk to affected systems.
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 workaround, avoid using the confluence_upload_attachment function until the package is updated. Ensure that only trusted clients have access to the Confluence pages where attachments can be uploaded.
Conclusion
The CVE-2026-77259 vulnerability in the mcp-atlassian package allows for arbitrary file reading through the confluence_upload_attachment function due to inadequate path validation. It is crucial for users to update to version 0.22.0 or later to mitigate this risk and protect sensitive information from potential exfiltration.
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FAQ
Any authenticated MCP client with edit access can read arbitrary files from the server, potentially exposing sensitive information such as API tokens and credentials.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
If an immediate update is not possible, restrict access to the affected functionality and monitor for any unauthorized access attempts.
Yes, you can limit the permissions of users who have access to upload attachments until the vulnerability is patched.
A CVSS score of 7.7 indicates a high severity vulnerability, suggesting that it poses a significant risk to the security of the affected system.
References
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