CVE-2026-77251
Received Received - Intake

MCP Atlassian Improper Project Filter Bypass

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, Jira search accepts a forbidden project clause because it checks only for the presence of project syntax, Confluence search uses an incomplete case-sensitive space check, and Jira board APIs omit project-filter enforcement. These paths expose issues, boards, or pages outside JIRA_PROJECTS_FILTER or CONFLUENCE_SPACES_FILTER when the operator credentials have broader access. The advisory traces the vulnerable input and processing flow through jira_search, confluence_search, get_board_issues, get_agile_boards, JIRA_PROJECTS_FILTER, and CONFLUENCE_SPACES_FILTER, 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-2026-77251
EUVD
EUVD-2026-84625

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
atlassian jira to 0.22.0 (exc)
atlassian confluence to 0.22.0 (exc)
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-1276 Signals between a hardware IP and the parent system design are incorrectly connected causing security risks.

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Executive Summary

This vulnerability involves three bugs in the mcp-atlassian package that allow unauthorized access to restricted projects or spaces despite configured allowlists. The flaws include a Jira search bypass via substring checks, a Confluence search bypass due to case-sensitive validation, and missing allowlist enforcement in Jira's agile board functions. These issues enable attackers to exfiltrate content from forbidden projects or spaces.

Detection Guidance

Check MCP Atlassian version with pip show mcp-atlassian. If version is below 0.22.0, the system is vulnerable. Review Jira and Confluence search queries for unauthorized project or space access patterns, such as case-sensitive uppercase project names in Confluence or substring matches in Jira JQL queries.

Impact Analysis

Attackers could exploit these bugs to access sensitive data in projects or spaces they are not authorized to view. This includes exfiltrating restricted content, especially in Atlassian Cloud deployments where Personal Access Tokens have broader permissions than the configured allowlist.

Compliance Impact

This vulnerability could lead to unauthorized data exposure, violating compliance requirements such as GDPR or HIPAA, which mandate strict access controls and data protection. Unauthorized access to sensitive information may result in regulatory penalties or breaches of confidentiality.

Mitigation Strategies

Upgrade MCP Atlassian to version 0.22.0 or later immediately. Replace substring-based project validation with AST-based JQL/CQL parsers. Ensure default-deny policies for ambiguous queries and restrict PAT permissions to match allowlist scopes.

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