Summary
MCP Atlassian attachment upload tools accept local filesystem paths and transmit the referenced file contents to Jira or Confluence. In HTTP or multi-user deployments, a caller who can invoke these tools may read configuration files, credentials, mounted secrets, or other files accessible to the MCP server process.
Affected context
The issue occurs in deployments of MCP Atlassian where Jira or Confluence attachment upload functionality runs on a server and accepts caller- influenced file paths. Risk is higher when the server is exposed over HTTP, shared by multiple users, or has access to sensitive local files and mounted secrets. The vulnerable path flows through the attachment upload tools and the server-local filesystem.
Exploit preconditions
- Attack surface: Jira and Confluence attachment upload tools - Required access: Ability to invoke the relevant MCP tool, subject to any
authentication and authorization controls
- Trigger point: Processing the supplied file_path during attachment upload - Why exploitation is possible: The server resolves and reads a caller-
controlled local path without sufficiently restricting it to an approved
upload directory, allowing access across the client-to-server filesystem
boundary
Why this happens
The underlying bug is insufficient restriction and validation of a user-influenced filesystem path. A server-side upload operation treats the supplied path as an allowable local resource rather than as an opaque, constrained reference to an approved file. This maps to CWE-22, Improper Limitation of a Pathname to a Restricted Directory, because path resolution can escape the intended file boundary and expose files readable by the MCP process.
Potential impact
- An attacker may disclose application configuration and credentials.
- Mounted secrets or tokens could be exposed.
- Files readable by the MCP process could be transmitted to Atlassian.
- A compromised credential could enable follow-on access to connected services.
- Multi-user deployments could allow cross-tenant or cross-client data exposure.
General mitigation guidance
Mitigation generally focuses on removing caller control over server-local paths and enforcing a narrow file access boundary. Upload APIs can accept file content, managed object references, or opaque server-issued handles instead of arbitrary paths. Where filesystem access is necessary, applications can canonicalize paths, require containment within a dedicated non-sensitive upload directory, reject links and special files where appropriate, and apply strict allowlists. Authentication and per-user authorization should govern tool access, while the MCP process should run with least privilege, limited filesystem visibility, isolated credentials, and read-only access to unrelated resources.
How teams detect issues like this
Detection can include static analysis for file APIs that consume user-controlled path arguments, especially calls that open, read, or transmit files after direct propagation from tool parameters such as file_path. Code review should examine canonicalization, directory-containment checks, symlink handling, authorization boundaries, and HTTP or multi-user exposure. Runtime monitoring can alert on reads outside approved upload directories and unusual attachment destinations. Policy enforcement in CI can require restricted path wrappers and reject unrestricted filesystem access in network-facing tool handlers. Automated code-review tools may help identify these data-flow patterns.
