CVE-2026-77244

[mcp-atlassian] Authentication bypass in HTTP transport: AtlassianOpaqueTokenVerifier accepts any non-empty token

State: Published
Severity: 10.0 Critical
Published: Sep 22, 2026
Updated: Sep 23, 2026
Reserved: Aug 20, 2026

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the HTTP transport accepts requests without a verified user identity and downstream fetcher construction falls back to the operator's globally configured Jira or Confluence credentials. A network client that can reach the MCP endpoint can invoke Atlassian tools as the operator, including read and write operations available to that account. The advisory traces the vulnerable input and processing flow through UserTokenMiddleware, AtlassianOpaqueTokenVerifier, _get_fetcher, and streamable-http, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Scores

CVSS	Score	Vector	Source
3.1	10.0 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N	GitHub_M

Weaknesses

CWE-287 Improper Authentication
CWE-303 Incorrect Implementation of Authentication Algorithm
CWE-862 Missing Authorization

Affected Products

Product	Versions
mcp-atlassiansooperset	< 0.22.0Affected

References

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