CVE-2026-77248: Atlassian MCP unauthenticated arbitrary file read in upload_attachment

CVE-2026-77248 · Severity: high · CVSS 8.6 · Published 2026-09-22

The sooperset/mcp-atlassian integration for Atlassian products (Confluence, Jira) exposes file upload and download capabilities to unauthenticated network clients when deployed with the streamable-http transport. An attacker can read any file accessible to the server process—including the operator's Atlassian API token, environment secrets, SSH keys, and system files—by uploading them via the vulnerable upload_attachment tool and retrieving them, while also gaining unauthenticated access to all Atlassian read/write operations under the operator's privileged account.

Technologies: mcp-atlassian (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-77248 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-77248 being exploited in the wild.
How severe is CVE-2026-77248?
High severity, with a CVSS score of 8.6, 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-2026-77248?
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-2026-77248 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-77248?
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
    pip install "mcp-atlassian>=0.22.0"

Technical details

The vulnerability chains two separate flaws in mcp-atlassian's streamable-http transport deployment. First, the OAuth-proxy authentication provider is opt-in (disabled by default), and the transport binds to 0.0.0.0 without enforcing authentication—requests without an Authorization header bypass auth validation and fall back to the operator's global Atlassian credentials stored in .env, granting unauthenticated network clients full read/write access to all tools. Second, the upload_attachment tool (in both Confluence and Jira implementations) passes user-supplied file_path directly to open() without path validation or sanitization, enabling path traversal attacks. An unauthenticated attacker can read arbitrary files on the server host by uploading them and downloading them back, including /proc/self/environ (revealing Atlassian API tokens), .env files, SSH keys, and system files, while simultaneously performing any Atlassian operation as the operator's (often admin) principal. The download_attachment flow uses path validation (validate_safe_path) but upload_attachment does not. Patches and mitigations involve requiring authentication by default and applying path validation to upload_attachment.

Affected products

  • sooperset mcp-atlassian <=0.21.1

Identifiers

  • CVE-2026-77248
  • GHSA-cc5h-2pwp-pvcc
  • PYSEC-2026-4089

Timeline

  • 2026-09-22: disclosed: Advisory GHSA-cc5h-2pwp-pvcc published
  • 2026: other: CVE-2026-77248 assigned

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