CVE-2026-77251: mcp-atlassian Package Vulnerability Allows Forbidden Project Content Exfiltration
Summary
CVE-2026-77251: mcp-atlassian is a popular community MCP server wrapper exposing Jira / Confluence to MCP clients. Affects mcp-atlassian versions < 0.22.0. Fixed in 0.22.0. How to fix ↓
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Background
The mcp-atlassian package is a widely used community MCP server wrapper that facilitates interaction with Jira and Confluence for MCP clients. It allows operators to restrict access to specific projects and spaces through environment variables like JIRA_PROJECTS_FILTER and CONFLUENCE_SPACES_FILTER. However, due to certain vulnerabilities, these filters can be bypassed, leading to unauthorized access to sensitive content.
Vulnerability Detail
The vulnerability arises from three distinct sub-bugs within the mcp-atlassian package that allow attacker-controlled queries to access content from forbidden projects and spaces. The most critical issue is a substring-bypass in Jira's JQL search, where user-supplied queries are not properly validated against the allowlist. This allows attackers to retrieve information from projects that should be restricted. The vulnerability has been empirically demonstrated on production Atlassian Cloud environments, highlighting its severity and potential impact on data confidentiality.
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, operators can manually review and restrict access to sensitive projects and spaces until the package is updated. Additionally, consider implementing stricter access controls on the underlying Jira and Confluence instances.
Conclusion
The mcp-atlassian package has a critical vulnerability that allows unauthorized access to restricted project content. It is essential for operators to update to the patched version to mitigate the risk of data exfiltration. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
See every vulnerability recorded for mcp-atlassian →
FAQ
CVE-2026-77251 is a vulnerability in the mcp-atlassian package that allows unauthorized access to forbidden project content due to improper filtering mechanisms.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The CVSS score of this vulnerability is 8.3, indicating a high severity level.
If an immediate update is not possible, implement stricter access controls and monitor for any unauthorized access attempts.
For more information, you can reach out to the maintainers of the mcp-atlassian package or consult the community forums.
References
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