CVE-2026-77262 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, confluence_upload_attachment accepts an attacker-controlled file_path and does not apply the path restriction added for the earlier download vulnerability. A caller can traverse outside the workspace and upload arbitrary server-readable files to Confluence. The advisory traces the vulnerable input and processing flow through confluence_upload_attachment, file_path, and CVE-2026-27825, 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 as CVE-2026-27825 resides within MCP Atlassian, a Model Context Protocol server designed to facilitate interactions with Atlassian products such as Confluence and Jira. This security flaw specifically affects the confluence_upload_attachment function in versions prior to 0.22.0. The core technical issue stems from an improper restriction of file path inputs, which allows for directory traversal attacks. While a previous vulnerability related to downloading files had prompted developers to implement certain path restrictions, these controls were not consistently applied across all entry points within the application logic. Specifically, the upload functionality failed to enforce the same rigorous validation checks that were implemented for download operations, creating an inconsistency in security posture that attackers can exploit.
From a technical perspective, the vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory. The confluence_upload_attachment endpoint accepts a file_path parameter from the caller without adequately sanitizing or validating it against the expected workspace directory structure. Because the path restriction logic was omitted for this specific operation, an attacker can supply a maliciously crafted file path containing sequence characters such as dot-dot-slash sequences to escape the intended sandboxed environment. This allows the server to write files to arbitrary locations on the host system that are readable by the Confluence process user account. The lack of input validation means there is no mechanism to prevent relative or absolute paths from being resolved outside the designated workspace root, effectively bypassing the isolation mechanisms designed to protect the underlying file system.
The operational impact of this vulnerability is significant as it enables unauthorized file upload and potential server-side compromise. By uploading arbitrary files to locations accessible by the Confluence service, an attacker could place malicious scripts, configuration files with elevated privileges, or other payloads that interact with the application environment. If the uploaded files are executed or processed by subsequent system operations, this can lead to remote code execution, data exfiltration, or further lateral movement within the network infrastructure. The ability to write outside the workspace also poses a risk of overwriting critical configuration files or logs, potentially disrupting service availability or masking attacker activity through log manipulation. This aligns with ATT&CK techniques related to Command and Scripting Interpreter abuse as well as Defense Evasion via file system modifications.
Mitigation for this vulnerability requires immediate upgrading to version 0.22.0 of MCP Atlassian, where the developers have addressed the inconsistent application of path restrictions across different endpoints. In addition to updating software components, administrators should implement defense-in-depth strategies such as running the Confluence service with minimal privileges and utilizing operating system-level file integrity monitoring to detect unauthorized writes outside expected directories. Input validation frameworks should be audited to ensure that all user-controlled inputs involving file paths are strictly validated against allowlists or canonicalized before processing. Regular security assessments focusing on path traversal vulnerabilities in API endpoints will help identify similar inconsistencies in other parts of the application stack, ensuring a more robust security posture across all interaction points with Atlassian products.