MCP Atlassian: Unauthenticated arbitrary local file read via upload_attachment file_path, chained with missing auth on streamable-http transport

Exploitation

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

CVSS

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

EPSS

• CVE-2026-77248: 0.47% estimated exploitation activity in the next 30 days; percentile 41.10 (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 In the documented multi-user HTTP deployment (--transport streamable-http with global operator Atlassian credentials), sooperset/mcp-atlassian exposes all tools to unauthenticated network clients, and the uploadattachment tool reads an attacker-supplied filepath with no path validation. Chained, an unauthenticated network attacker reads arbitrary files on the MCP server host (e.g. /proc/self/environ → the operator's Atlassian API token + .env secrets, ~/.ssh/idrsa, /etc/passwd) by uploading them to an attacker-chosen page/issue and reading them back. Details Missing authentication (transport): - streamable-http binds 0.0.0.0 by default (src/mcpatlassian/init.py:151). - The OAuth-proxy auth provider is opt-in (ATLASSIANOAUTHPROXYENABLE, default false), so mainmcp is built with auth=None (src/mcpatlassian/servers/main.py:724-731, 813-817). - UserTokenMiddleware.parseauthheader sets authvalidationerror only for a malformed Authorization header; a request with no Authorization…

Published by the source

22 Sep 2026, 20:34 UTC

Last modified by the source

1 Oct 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:54 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cc5h-2pwp-pvcc

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-cc5h-2pwp-pvcc

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-cc5h-2pwp-pvcc

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# Patch Next advisory brief: CVE-2026-77248

Advisory: MCP Atlassian: Unauthenticated arbitrary local file read via upload_attachment file_path, chained with missing auth on streamable-http transport
IDs: CVE-2026-77248, GHSA-cc5h-2pwp-pvcc
Record: https://patchnext.com/advisories/cve-2026-77248 (revision 3, source checked 26 Oct 2026, 13:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-atlassian 0.22.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-atlassian: affected < 0.22.0; fixed in 0.22.0

## 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-cc5h-2pwp-pvcc (GitHub-reviewed advisory GHSA-cc5h-2pwp-pvcc lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0)
- Verified: https://osv.dev/vulnerability/GHSA-cc5h-2pwp-pvcc (OSV record GHSA-cc5h-2pwp-pvcc lists affected ranges: PyPI mcp-atlassian >=0 <0.22.0 (fixed))

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