23 Oct 2026 15:48:27 UTC
MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions
cve-program · CVE-2026-77250 · Published
CVE-2026-77250
mcp-atlassian · Vulnerability
CVSS 3.1 6.1 MEDIUMCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-77250
PublishedMCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, OAuthConfig writes a plaintext fallback file containing access and refresh tokens under the user's .mcp-atlassian directory using process-default permissions. On systems with a permissive umask, same-group or other local users and processes can read the persisted tokens and reuse the associated Atlassian access. The advisory traces the vulnerable input and processing flow through OAuthConfig._save_tokens, ~/.mcp-atlassian/oauth-<client_id>.json, access_token, and refresh_token, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.
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