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Authorization bypass via MCP endpoint

Moderate
klaustopher published GHSA-w9w6-f59w-89vj Feb 26, 2026

Software

OpenProject

Affected versions

< 17.0.5

Patched versions

17.0.5, 17.1.2

Description

If the MCP server is enabled in the application, users that do not have access to enumerate Status or Types could access those resources without proper permission checks via the MCP server.

Credits

This vulnerability was reported by users noidont and syndrome_impostor as part of the YesWeHack.com OpenProject Bug Bounty program, sponsored by the European Commission.

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVE ID

CVE-2026-27733

Weaknesses

No CWEs