CVE-2026-77260 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 Confluence and Jira upload_attachment implementations accept an unconstrained file_path and open the referenced server-local file. A permitted MCP caller can upload sensitive host files to an Atlassian destination and then retrieve their contents. The advisory traces the vulnerable input and processing flow through 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.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified as CVE-2026-27825 represents a critical path traversal and arbitrary file read flaw within MCP Atlassian, specifically affecting versions prior to 0.22.0. This software serves as an implementation of the Model Context Protocol for interacting with Atlassian products such as Confluence and Jira. The core technical deficiency lies in the upload_attachment function, which is designed to facilitate the transfer of files into these platforms. However, the implementation fails to adequately sanitize or validate the file_path parameter provided by the caller. Instead of restricting access to a designated directory or validating that the requested path resides within an allowed scope, the application directly passes this unconstrained input to underlying system calls responsible for opening and reading local server files. This lack of validation allows any permitted MCP client to specify arbitrary absolute paths on the host operating system where the Atlassian instance is running.
From a technical perspective, this flaw constitutes a classic Path Traversal vulnerability, categorized under CWE-22: Improper Limitation of a Pathname to a Restricted Directory in standard security taxonomies. By supplying maliciously crafted file paths such as /etc/passwd or sensitive configuration files containing API keys and database credentials, an attacker can bypass intended access controls. The operational impact is severe because it enables unauthorized data exfiltration from the server hosting the Atlassian application. An adversary with valid authentication to the MCP interface does not need to exploit a separate remote code execution vulnerability; they can directly read sensitive host files by leveraging this endpoint. This capability effectively turns the upload feature into a powerful information disclosure vector, potentially leading to further compromise of the broader infrastructure if critical secrets are exposed.
In terms of threat modeling and adversary behavior, this vulnerability aligns with ATT&CK technique T1083: File and Directory Discovery, as well as T1560: Archive Collected Data, since the attacker retrieves specific files from the system to gather intelligence or exfiltrate data. The attack chain is straightforward for any authenticated user of the MCP service, requiring no complex exploitation steps beyond crafting a request with a malicious file_path argument. This simplicity increases the likelihood of successful exploitation in environments where internal services are trusted but not strictly isolated.
To mitigate this vulnerability, organizations must immediately upgrade to version 0.22.0 or later of MCP Atlassian, which addresses these input validation gaps by implementing strict path canonicalization and directory confinement checks before processing file operations. Until an upgrade is feasible, administrators should restrict network access to the MCP endpoint to only those clients that are strictly necessary for business functions, thereby limiting the attack surface. Additionally, deploying a Web Application Firewall with rules capable of detecting common path traversal patterns may provide a layer of defense in depth, although this is not a substitute for proper code-level remediation. Regular auditing of file access logs on the Atlassian server can also help detect attempts to read sensitive system files via this vector.