What’s Vulnerable › Vulnerabilities

CVE-2026-77268: MCP Atlassian: Insecure File Permissions on OAuth Token Storage

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-22 · updated 2026-09-29
• Weakness: CWE-732

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.

Affected products

• sooperset mcp-atlassian: before 0.22.0 — fixed in 0.22.0

How to fix

Upgrade to a fixed version: sooperset mcp-atlassian 0.22.0. Check the vendor advisory for mitigations.

References

• https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
• https://github.com/sooperset/mcp-atlassian/pull/1448
• https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0
• https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-4596-2p6p-28cv

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