CVE-2026-77250: MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions
When OAuth tokens are saved, MCP Atlassian always writes a plaintext fallback copy under ~/.mcp-atlassian/oauth-<client_id>.json. The fallback file is created with the process default umask rather than restrictive permissions. In this environment the file was created as mode 0664, exposing access and refresh tokens to same-group local users and any process that can read the home directory.
References
- github.com/advisories/GHSA-g5xv-mhgm-v5f6
- github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
- github.com/sooperset/mcp-atlassian/pull/1448
- github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0
- github.com/sooperset/mcp-atlassian/security/advisories/GHSA-g5xv-mhgm-v5f6
- nvd.nist.gov/vuln/detail/CVE-2026-77250
Code Behaviors & Features
Detect and mitigate CVE-2026-77250 with GitLab Dependency Scanning
Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Learn more about Dependency Scanning →