CVE-2026-77250
Received Received - Intake

Information Disclosure in MCP Atlassian OAuth Tokens

Publication date: 2026-09-22

Last updated on: 2026-09-22

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-09-22
Last Modified
2026-09-22
Generated
2026-09-22
AI Q&A
2026-09-22
EPSS Evaluated
N/A
NVD
CVE-2026-77250
EUVD
EUVD-2026-84619

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
atlassian mcp to 0.22.0 (exc)
atlassian mcp-atlassian to 0.22.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-312 The product stores sensitive information in cleartext within a resource that might be accessible to another control sphere.

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Executive Summary

This vulnerability involves the mcp-atlassian package storing OAuth tokens in plaintext files with insecure permissions. When tokens are saved, they are written to a file like ~/.mcp-atlassian/oauth-<client_id>.json with default umask permissions (e.g., 0664), making them readable by other users on the same system. This exposes access and refresh tokens to local attackers or processes with filesystem access.

Detection Guidance

Check for plaintext OAuth token files in ~/.mcp-atlassian/oauth-<client_id>.json. Verify file permissions with 'ls -l ~/.mcp-atlassian/oauth-*.json' to see if they are readable by others. Search for files modified before version 0.22.0 using 'find ~/.mcp-atlassian -name "oauth-*.json" -type f'.

Impact Analysis

An attacker with access to the plaintext token file could reuse the stolen access or refresh tokens to gain unauthorized access to your Atlassian accounts (Confluence or Jira). This could lead to data theft, unauthorized modifications, or persistent account compromise if refresh tokens are obtained.

Compliance Impact

This vulnerability likely violates compliance requirements for data protection (e.g., GDPR, HIPAA) due to unauthorized access to sensitive credentials. It exposes protected data to unauthorized parties, potentially leading to breaches of confidentiality and integrity requirements.

Mitigation Strategies

Upgrade mcp-atlassian to version 0.22.0 or later. Remove any existing plaintext token files in ~/.mcp-atlassian/oauth-*.json. Revoke compromised Atlassian tokens via your Atlassian account settings and regenerate new ones.

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