MCP Atlassian has an arbitrary file write leading to arbitrary code execution via unconstrained download_path in confluence_download_attachment

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.0 · CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS

• CVE-2026-27825: 11.50% estimated exploitation activity in the next 30 days; percentile 96.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The confluencedownloadattachment MCP tool accepts a downloadpath parameter that is written to without any directory boundary enforcement. An attacker who can call this tool and supply or access a Confluence attachment with malicious content can write arbitrary content to any path the server process has write access to. Because the attacker controls both the write destination and the written content (via an uploaded Confluence attachment), this constitutes for arbitrary code execution (for example, writing a valid cron entry to /etc/cron.d/ achieves code execution within one scheduler cycle with no server restart required). Details The tool parameter is defined in src/mcpatlassian/servers/confluence.py:~1275 without any path restriction: python downloadpath: Annotated str, Field( description=( "Full path where the file should be saved. Can be absolute or relative. " "Examples: './downloads/report.pdf', '/tmp/image.png', 'C:\\\\temp\\\\file.docx'. " "Parent directory will be…

Published by the source

10 Mar 2026, 18:56 UTC

Last modified by the source

29 Jun 2026, 12:26 UTC

Source last checked

26 Oct 2026, 13:37 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xjgw-4wvw-rgm4

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-xjgw-4wvw-rgm4

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-xjgw-4wvw-rgm4

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# Patch Next advisory brief: CVE-2026-27825

Advisory: MCP Atlassian has an arbitrary file write leading to arbitrary code execution via unconstrained download_path in confluence_download_attachment
IDs: CVE-2026-27825, GHSA-xjgw-4wvw-rgm4
Record: https://patchnext.com/advisories/cve-2026-27825 (revision 3, source checked 26 Oct 2026, 13:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-atlassian 0.17.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-atlassian: affected < 0.17.0; fixed in 0.17.0

## Suggested inspection (read-only)
- `python -m pip show mcp-atlassian`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mcp-atlassian.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xjgw-4wvw-rgm4 (GitHub-reviewed advisory GHSA-xjgw-4wvw-rgm4 lists affected ranges: PyPI mcp-atlassian >=0 <0.17.0)
- Verified: https://osv.dev/vulnerability/GHSA-xjgw-4wvw-rgm4 (OSV record GHSA-xjgw-4wvw-rgm4 lists affected ranges: PyPI mcp-atlassian >=0 <0.17.0 (fixed))

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