# CVE-2026-77259: MCP Atlassian arbitrary file read via confluence_upload_attachment

Source: https://junglewise.ai/threats/cve-2026-77259-mcp-atlassian-arbitrary-file-read-via-confluence-upload  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77259 · Severity: high · CVSS 7.7 · Published 2026-09-22

MCP Atlassian is a tool that integrates Atlassian products (Confluence, Jira) with AI assistants. The upload_attachment feature fails to validate file paths, allowing any authenticated user with edit access to read arbitrary files from the server—including sensitive configuration files and credential stores. In cloud or containerized deployments, attackers can extract API tokens and credentials needed for persistent unauthorized access to Atlassian infrastructure.

Technologies: [mcp-atlassian (PyPI)](https://junglewise.ai/threats/technologies/mcp-atlassian). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-77259 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77259 being exploited in the wild.

**How severe is CVE-2026-77259?** High severity, with a CVSS score of 7.7, published 22 September 2026.

**Which products and versions are affected?** mcp-atlassian (PyPI) < 0.22.0, ECOSYSTEM:introduced=0,fixed=0.22.0.

**Is there a fix for CVE-2026-77259?** Yes. mcp-atlassian (PyPI): upgrade to 0.22.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77259 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-77259?** Check whether you run mcp-atlassian (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- mcp-atlassian (PyPI): upgrade to 0.22.0 or later

  ```sh
  pip install "mcp-atlassian>=0.22.0"
  ```


## Technical details

The vulnerability exists in `AttachmentsMixin.upload_attachment()` in src/mcp_atlassian/confluence/attachments.py (line 477), which opens a caller-supplied file path without boundary validation. While a similar download path vulnerability (GHSA-xjgw-4wvw-rgm4) was previously fixed using a `validate_safe_path()` function, the upload path was left unguarded. An authenticated MCP client with edit access to any Confluence page can exploit this to read arbitrary files. On Linux, direct access to `/proc/self/environ` exposes all runtime secrets. The fix requires applying the existing `validate_safe_path()` validation to the upload and upload_attachments functions, as well as corresponding Jira attachment handlers.

## Affected products

- Atlassian MCP Atlassian 0.21.1 and earlier

## Identifiers

- CVE-2026-77259
- GHSA-6cr4-ccf3-x7h4
- PYSEC-2026-4086

## Timeline

- 2026-09-22: disclosed: GHSA-6cr4-ccf3-x7h4 published
- 2026: other: CVE-2026-77259 assigned

## Related threats

- [Atlassian MCP reflected XSS in OAuth setup callback handler](https://junglewise.ai/threats/cve-2026-77272-atlassian-mcp-reflected-xss-in-oauth-setup-callback-handler)
- [Atlassian MCP path traversal in upload_attachment allows arbitrary file read](https://junglewise.ai/threats/cve-2026-77269-atlassian-mcp-path-traversal-in-upload-attachment-allows)
- [Atlassian MCP insecure OAuth token file permissions](https://junglewise.ai/threats/cve-2026-77268-atlassian-mcp-insecure-oauth-token-file-permissions)
- [MCP Atlassian path traversal in upload_attachment](https://junglewise.ai/threats/cve-2026-77266-mcp-atlassian-path-traversal-in-upload-attachment)
- [sooperset mcp-atlassian path traversal in confluence_upload_attachment](https://junglewise.ai/threats/cve-2026-77262-sooperset-mcp-atlassian-path-traversal-in-confluence-upload)