CVE-2026-77244
Received Received - Intake

Authentication Bypass in MCP Atlassian Prior to 0.22.0

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 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.

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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-2026-77244
EUVD
EUVD-2026-84607

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
atlassian mcp to 0.22.0 (exc)
atlassian confluence *
atlassian jira *
atlassian mcp-atlassian to 0.22.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-862 The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
CWE-287 When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
CWE-303 The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.

Attack-Flow Graph

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Executive Summary

CVE-2026-77244 is a critical authentication bypass in MCP Atlassian versions before 0.22.0. It allows unauthenticated attackers with network access to the HTTP transport to gain full operator-level access to Jira and Confluence using the server's configured credentials. The vulnerability occurs because the server accepts requests without verified user identity and falls back to global credentials when no valid token is provided.

Detection Guidance

Check if your mcp-atlassian version is below 0.22.0 by running: pip show mcp-atlassian. If installed via Docker, verify the image tag. Inspect network traffic for requests to the MCP HTTP transport endpoint without an Authorization header or with invalid tokens.

Impact Analysis

An attacker can read, modify, or delete data in your Atlassian instances (Jira/Confluence) without authentication. They can perform actions as the operator account, including creating persistent access via webhooks or automation rules. Exploitation requires only network access to the HTTP transport endpoint.

Compliance Impact

This vulnerability likely violates compliance requirements for data protection (GDPR, HIPAA) due to unauthorized access to sensitive data. It enables full confidentiality and integrity breaches, as attackers can exfiltrate, alter, or destroy regulated data without detection.

Mitigation Strategies

Upgrade to mcp-atlassian version 0.22.0 or later immediately. Disable HTTP transport if not required or bind it to localhost. Enable OAuth proxy authentication and ensure the server rejects requests without valid tokens.

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