https://vulnerability.circl.lu/rss/recent/all/10 Most recent entries from all 2026-10-02T14:15:23.023714+00:00 Vulnerability-Lookup info@circl.lu python-feedgen Contains only the most 10 recent entries. https://vulnerability.circl.lu/vuln/cve-2026-77250 CVE-2026-77250 — MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions 2026-10-02T14:15:23.329515+00:00

Affected: sooperset mcp-atlassian

MCP 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.

 https://vulnerability.circl.lu/vuln/pysec-2026-4094 PYSEC-2026-4094 — MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions 2026-10-02T14:15:23.329630+00:00

Affected: PyPI: mcp-atlassian

### Summary

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.

### Details

`OAuthConfig._save_tokens()` stores OAuth token data in keyring, but it also unconditionally maintains a plaintext file fallback for backwards compatibility in `src/mcp_atlassian/utils/oauth.py:350-386`. If keyring saving fails it also falls back to the same file path in `src/mcp_atlassian/utils/oauth.py:387-391`.

The fallback writer creates `~/.mcp-atlassian` and then writes `oauth-<client_id>.json` with a normal `open(token_path, "w")` call in `src/mcp_atlassian/utils/oauth.py:392-420`. No `mode=0o600`, `os.open(..., 0o600)`, `chmod`, or owner-only directory permission is applied. The file contains both `access_token` and `refresh_token` (`src/mcp_atlassian/utils/oauth.py:360-367`) and is later loaded from the same plaintext path in `src/mcp_atlassian/utils/oauth.py:450-470`.

The security policy warns that OAuth client credentials and secrets should not be exposed (`SECURITY.md:39-44`), but the current implementation creates a persistent plaintext token copy even when keyring succeeds.

### PoC

The following safe local proof uses a temporary `HOME` and m…