CVE-2026-77270 in mcp-atlassian
Summary
by MITRE • 09/22/2026
MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the Jira and Confluence attachment upload tools treat caller-controlled file_path values as trusted server-local paths. The server opens the selected file and uploads it to an Atlassian issue or page, allowing an MCP caller with upload access to disclose any file readable by the server process. The advisory traces the vulnerable input and processing flow through confluence_upload_attachment, jira_upload_attachment, file_path, and open(file_path, "rb"), which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified within MCP Atlassian versions prior to 0.22.0 represents a critical server-side file inclusion flaw rooted in improper input validation of caller-controlled parameters. As a Model Context Protocol server designed to interface with Atlassian products such as Confluence and Jira, the application handles sensitive operations including attachment uploads. The core technical defect lies in how the system processes the file_path argument provided by the client during upload requests for both confluence_upload_attachment and jira_upload_attachment functions. Instead of validating or sanitizing this input to ensure it resides within an expected directory structure or adheres to a whitelist of permissible files, the server treats the caller-supplied path as a trusted local filesystem location. This architectural oversight allows any file readable by the operating system user running the MCP Atlassian process to be selected for upload, bypassing intended access controls and exposing internal data structures that should remain isolated from external clients.
From an operational perspective, this flaw enables unauthorized information disclosure with significant severity implications. An attacker or malicious actor who has obtained valid credentials or API tokens granting them permission to upload attachments can exploit the file_path parameter to read arbitrary files from the server's local filesystem. This capability extends beyond application-specific data to include configuration files containing database credentials, private keys, environment variables, source code, and other sensitive artifacts stored on the host machine. The impact is compounded by the fact that the vulnerability does not require privilege escalation or remote code execution; it relies solely on existing upload permissions which are often granted to a broader set of users than necessary for such low-level filesystem access. Consequently, this represents a severe breach of confidentiality within the Atlassian ecosystem integration layer, potentially leading to further compromise if sensitive credentials found in these files are leveraged against other systems.
In terms of industry standard classifications, this vulnerability aligns with CWE-22: Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal or directory traversal. The failure to restrict file access to a specific sandboxed area allows the application to escape its intended operational boundaries and interact with arbitrary parts of the host filesystem. Furthermore, this behavior facilitates unauthorized data exfiltration which can be categorized under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor. In the context of the MITRE ATT&CK framework, this vulnerability supports techniques related to Collection from Local System Sources (T1005) and potentially Data Staged for Exfiltration if the uploaded files are subsequently transmitted out of the network via the Atlassian platform itself. The attack vector is primarily local or internal depending on how the MCP server is exposed, but it fundamentally exploits a lack of input validation in file handling routines.
The remediation strategy involves upgrading to version 0.22.0 where this issue has been resolved through rigorous input sanitization and path canonicalization techniques. Developers implementing similar integrations should ensure that all user-supplied file paths are normalized using standard library functions such as os.path.realpath or equivalent mechanisms in other languages to resolve symbolic links and relative references before any filesystem operations occur. It is critical to implement a strict allowlist of permitted directories, ensuring that the resolved absolute path starts with the expected base directory prefix. Additionally, principle of least privilege should be applied by running the MCP server process under a restricted user account with minimal file system permissions, thereby limiting the blast radius even if such vulnerabilities are present in future versions. Regular security audits and static analysis tools configured to detect unsafe open calls without proper validation can help identify similar patterns early in the development lifecycle.