# CVE-2026-77246: MCP Atlassian HTTP server local file exfiltration via unvalidated attachment path

Source: https://junglewise.ai/threats/cve-2026-77246-mcp-atlassian-http-server-local-file-exfiltration-via-unvalidated  
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-2026-77246 · Severity: high · CVSS 7.4 · Published 2026-09-22

The MCP Atlassian server, when deployed in HTTP transport mode, accepts arbitrary file paths in attachment upload tools without validation. An unauthenticated attacker can supply forged Atlassian service headers to redirect uploads to an attacker-controlled endpoint and exfiltrate sensitive files (credentials, SSH keys, environment files) readable by the server process. No authentication or authorization headers are required.

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

## Quick answers

**Is CVE-2026-77246 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77246 being exploited in the wild.

**How severe is CVE-2026-77246?** High severity, with a CVSS score of 7.4, 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-2026-77246?** 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-2026-77246 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-77246?** 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 is a server-side file exfiltration (CWE-200) in the `confluence_upload_attachment` and `jira_upload_attachment` MCP tools. The attack chain combines three weaknesses: (1) HTTP header-based "authentication" that bypasses authorization when no Authorization header is present and attacker-supplied `X-Atlassian-Confluence-Url` / `X-Atlassian-Confluence-Personal-Token` headers are provided; (2) insufficient SSRF validation that permits attacker-controlled domains; and (3) absence of path sanitization in the attachment upload code path (while the download path correctly calls `validate_safe_path()`). The file_path argument is converted to an absolute path via `os.path.abspath()` but never restricted to a safe directory, allowing reads of `/etc/passwd`, `~/.env`, SSH keys, and cloud credentials. The vulnerability requires HTTP transport mode and `READ_ONLY_MODE=false` (both defaults in documented deployments), but no prior authentication.

## Affected products

- Atlassian MCP Atlassian Prior to patch (commit d8bc786)

## Identifiers

- CVE-2026-77246
- GHSA-wv8v-v4c5-v75j
- PYSEC-2026-4104

## Timeline

- 2026-09-22: disclosed: GHSA-wv8v-v4c5-v75j published
- 2026: other: CVE-2026-77246 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)