CVE-2026-77254

CRITICAL CVSS 3.1: 9.1 EPSS 0.62%
Updated Sep 28, 2026
Mcp-Atlassian
Parameter Value
CVSS 9.1 (CRITICAL)
Affected Versions before 0.22.0
Fixed In 0.22.0
Type CWE-306 (Missing Authentication for Critical Function)
Vendor Mcp-Atlassian
Public PoC No

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, requests to the HTTP MCP endpoint without a per-user identity are allowed to reach tool handlers, which then use globally configured Jira or Confluence credentials. A network caller can perform operations with the operator account's permissions unless the deployment has an independent authentication boundary.

The advisory traces the vulnerable input and processing flow through streamable-http, UserTokenMiddleware, _get_fetcher, and global credentials, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption

CVSS Vector v3.1

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Mcp-Atlassian Mcp_Atlassian
cpe:2.3:a:mcp-atlassian:mcp_atlassian:*:*:*:*:*:*:*:*
— 0.22.0