CVE-2026-77268
Received Received - Intake

MCP Atlassian OAuth Token Exposure via Weak File Permissions

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, the OAuth fallback token directory and JSON file are created without explicit owner-only modes. Local users or processes with access through the resulting group or world permission bits can read access and refresh tokens and reuse the associated Atlassian session. The advisory traces the vulnerable input and processing flow through ~/.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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

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-2026-77268
EUVD
EUVD-2026-84757

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
atlassian mcp-atlassian 0.22.0
atlassian mcp 0.22.0

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-732 The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability involves insecure file permissions in the mcp-atlassian package affecting OAuth token storage. Token files are created with default permissions (0644) instead of restrictive ones, allowing local users on shared systems to read access tokens, refresh tokens, and cloud IDs. These tokens can be reused to gain unauthorized access to Atlassian APIs like Jira and Confluence.

Detection Guidance

Check for world-readable OAuth token files in ~/.mcp-atlassian/oauth-<client_id>.json and related token files. Use commands like 'ls -la ~/.mcp-atlassian/' to inspect permissions. Look for files with permissions 0644 or less restrictive than 0600.

Impact Analysis

An attacker with local access to a shared system could read OAuth tokens and reuse them to access your Atlassian accounts without authorization. This includes persistent access via refresh tokens, which can generate new access tokens indefinitely, compromising confidentiality and potentially leading to data breaches.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. Exposure of tokens may result in data breaches, triggering compliance violations, fines, or legal consequences due to inadequate access controls.

Mitigation Strategies

Update mcp-atlassian to version 0.22.0 or later. Manually set restrictive permissions on existing token files and directories using 'chmod 0700 ~/.mcp-atlassian' and 'chmod 0600 ~/.mcp-atlassian/oauth-*.json'. Remove any unnecessary local user access to shared systems.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-77268. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart