CVE-2026-77256
MCP Atlassian: OAuth refresh-token backup file is world-readable under default Unix umask
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Description
MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the plaintext OAuth fallback file containing refresh and access tokens is written with permissions inherited from the process umask. Under common or permissive configurations, other local users can read the backup and retain Atlassian access through the refresh token. The advisory traces the vulnerable input and processing flow through OAuthConfig._save_tokens_to_file, refresh_token, access_token, and umask, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.
Affected
Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.
Remediation
No guide yetNo remediation guidance has been written for this CVE yet. What the record does show:
References (4)
SSVC — Action Prioritization
SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.
CVSS
- Attack Vector
- NETWORK
- Complexity
- LOW
- Privileges
- LOW
- User Interaction
- NONE
- Scope
- UNCHANGED
- Confidentiality
- HIGH
- Integrity
- NONE
- Availability
- NONE
Quick Info
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