CVE-2026-77247 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, Jira and Confluence upload tools interpret caller-controlled path arguments on the MCP server and open those files before sending them as attachments. In remote or multi-user deployments, a permitted client can disclose host files without shell or direct filesystem access. The advisory traces the vulnerable input and processing flow through AttachmentsMixin.upload_attachment, AttachmentsMixin.upload_attachments, file_path, file_paths, and jira update_issue, 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 in MCP Atlassian prior to version 0.22.0 represents a critical path traversal and unauthorized file disclosure flaw within the Model Context Protocol server implementation for Atlassian products such as Confluence and Jira. This security issue stems from an insufficient validation of user-supplied input during the file upload process, specifically affecting how the server handles caller-controlled path arguments intended for attaching files to issues or pages. In remote or multi-user deployment scenarios, this flaw allows a permitted client to read arbitrary files from the host system where the MCP server is running, effectively bypassing standard access controls that would normally restrict such operations without shell access or direct filesystem permissions.
The technical root cause lies in the improper handling of file paths within the AttachmentsMixin class methods, specifically upload_attachment and upload_attachments. When a client requests to attach a file, these functions accept a file_path argument provided by the caller. Instead of strictly validating that this path resides within an expected or allowed directory structure, the server directly interprets the input string as a filesystem location. This lack of sanitization enables attackers to utilize standard path traversal sequences, such as dot-dot-slash patterns, to navigate up the directory hierarchy and access sensitive system files located outside the intended application scope. The vulnerability is further exacerbated by the integration points with Jira update_issue operations, which serve as entry points for triggering these vulnerable code paths during routine issue management tasks.
From an operational impact perspective, this vulnerability facilitates unauthorized data exfiltration on a scale that can compromise the entire infrastructure hosting the Atlassian instance. An attacker who has valid credentials to interact with the MCP server can enumerate and read sensitive configuration files, environment variables containing secrets or API keys, source code repositories, database connection strings, and other critical system artifacts. This capability effectively neutralizes network-based security controls since the attack vector operates through legitimate application APIs rather than exploiting external-facing services directly. The ability to disclose host files without requiring elevated privileges or command execution capabilities makes this a high-severity risk that can lead to full system compromise when combined with subsequent exploitation techniques targeting extracted credentials or configuration data.
This vulnerability aligns closely with CWE-22, which defines Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal. The attack methodology corresponds to ATT&CK technique T1083, File and Directory Discovery, where adversaries probe the target system for files and directories that may contain sensitive information. Furthermore, because the exploitation occurs through authenticated API interactions rather than unauthenticated network probes, it also reflects aspects of CWE-269, Improper Privilege Context Management, as a lower-privileged user leverages application functionality to achieve effects typically reserved for higher-privilege contexts or local system access.
To mitigate this vulnerability, organizations must immediately upgrade the MCP Atlassian server to version 0.22.0 or later, where the developers have implemented proper input validation and path canonicalization checks. Until upgrading is feasible, administrators should restrict network access to the MCP server endpoints to only trusted internal clients with minimal required permissions. Implementing strict file upload restrictions that limit accepted extensions and enforce directory containment policies can also reduce exposure. Additionally, deploying web application firewalls configured to detect and block common path traversal patterns in API requests may provide a temporary layer of defense against exploitation attempts targeting this specific flaw.