Summary
MCP Atlassian contains a path traversal vulnerability in the Confluence and Jira
attachment upload functions. A permitted MCP caller may cause a server-local file
to be opened and uploaded to an Atlassian destination, potentially exposing
sensitive host data when the attachment is later accessible.
Affected context
The issue occurs in deployments of MCP Atlassian where the Confluence or Jira
upload_attachment implementation accepts a caller-controlled file_path.
Risk depends on the MCP caller being authorized to invoke the upload operation
and the server process having access to sensitive local files. The vulnerable
behavior is associated with the file-opening and attachment-upload code path.
Exploit preconditions
- Attack surface: MCP tool endpoints that expose Confluence or Jira attachment uploads
- Required access: Permission to invoke the relevant MCP upload operation
- Trigger point: Processing of the
file_pathargument byupload_attachment - Why exploitation is possible: The supplied path is not sufficiently constrained
to the intended file area before the server opens the referenced local file
- Additional condition: The MCP server identity must be able to read the targeted file,
and the Atlassian destination must permit the resulting attachment to be uploaded or viewed
Why this happens
The underlying bug is improper restriction of a filesystem path supplied through an
MCP request. The upload implementation treats the path as a usable local file
reference without reliably constraining it to an approved directory or validating
the resolved location. This behavior maps to CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), because an attacker may
influence which server-local file is accessed.
Potential impact
- Sensitive configuration, credential, or application files may be disclosed
- Files readable by the MCP server process could be uploaded to an Atlassian project
- Exposed data may be retained in attachment history or downstream backups
- The incident could enable follow-on compromise if uploaded files contain secrets
- Audit, privacy, or compliance obligations may be affected
General mitigation guidance
Mitigation generally focuses on reducing trust in caller-supplied paths and
enforcing a narrow file-access policy.
Common defensive patterns include:
- Accepting opaque server-managed file references instead of arbitrary filesystem paths
- Restricting readable files to a dedicated allowlisted directory
- Canonicalizing paths before access and verifying that the resolved path remains within
the permitted directory
- Rejecting traversal components, symbolic-link escapes, device files, and unexpected file types
- Applying strict size, type, and destination controls to attachments
- Running the MCP server with a dedicated least-privilege identity and minimal filesystem access
- Avoiding storage of credentials and other sensitive material in directories readable by the service
- Logging file-reference decisions and attachment uploads for review
How teams detect issues like this
Detection approaches can include:
- Static analysis for direct use of request-derived path values in file-opening APIs
- Code review checks for missing canonicalization and directory-boundary validation
- Tests covering traversal components, absolute paths, symbolic links, and alternate path forms
- Runtime policies that alert when an MCP upload references files outside an approved workspace
- Monitoring attachment uploads for unusual filenames, destinations, sizes, or access patterns
- Automated security review tools that identify filesystem path flows from MCP arguments
