CVE-2026-27826: mcp-atlassian SSRF Vulnerability via Unvalidated Headers
Summary
CVE-2026-27826: MCP Atlassian has SSRF via unvalidated X-Atlassian-Jira-Url / X-Atlassian-Confluence-Url headers. Affects mcp-atlassian versions < 0.17.0. Fixed in 0.17.0. How to fix ↓
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Background
mcp-atlassian is a Python package that facilitates integration with Atlassian products like Jira and Confluence. It allows users to interact with these services through a multi-tenant HTTP interface. However, due to a flaw in its HTTP middleware, the package is vulnerable to Server-Side Request Forgery (SSRF), which can lead to unauthorized access to internal resources.
Vulnerability Detail
The vulnerability arises from the lack of validation for the 'X-Atlassian-Jira-Url' and 'X-Atlassian-Confluence-Url' headers in the mcp-atlassian package. An unauthenticated attacker can exploit this by sending crafted requests to the mcp-atlassian HTTP endpoint, allowing the server to make outbound requests to arbitrary URLs. This can lead to internal network reconnaissance, potential theft of sensitive data, and injection of malicious content into responses from the Jira or Confluence APIs.
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
0.17.0
This is the first release that contains the fix.
pip install --upgrade "mcp-atlassian==0.17.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can disable the use of the 'X-Atlassian-Jira-Url' and 'X-Atlassian-Confluence-Url' headers in your requests until you can update the package. Ensure that your application does not allow unauthenticated access to the mcp-atlassian HTTP endpoint.
Conclusion
The mcp-atlassian package is vulnerable to SSRF due to unvalidated headers, which can lead to serious security risks. It is crucial to update to the patched version to mitigate these risks and ensure the security of your application.
See every vulnerability recorded for mcp-atlassian →
FAQ
Server-Side Request Forgery (SSRF) is a vulnerability that allows an attacker to send crafted requests from a vulnerable server to internal or external resources, potentially leading to unauthorized access.
You can check if your application is affected by using the Vulert playground at Vulert Scanner, which monitors and alerts for open-source vulnerabilities in real-time.
The impacts include unauthorized access to internal services, potential data theft, and the ability to inject malicious content into API responses.
Yes, the vulnerability has been patched in version 0.17.0 of the mcp-atlassian package. It is recommended to update to this version or later.
If immediate updates are not possible, consider implementing a temporary workaround by disabling the use of the vulnerable headers and restricting unauthenticated access to the HTTP endpoint.
References
Related vulnerabilities
Recent vulnerabilities recorded for mcp-atlassian.
