CVE-2025-8533 in Fantastical
Summary
by MITRE • 08/07/2025
A vulnerability was identified in the XPC services of Fantastical. The services failed to implement proper client authorization checks in its listener:shouldAcceptNewConnection method, unconditionally accepting requests from any local process. As a result, any local, unprivileged process could connect to the XPC service and access its methods.
This issue has been resolved in version 4.0.16.
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Analysis
by VulDB Data Team • 08/07/2025
The vulnerability identified as CVE-2025-8533 resides within the XPC services of Fantastical, a macOS calendar application that provides advanced scheduling and reminder functionalities. XPC (Cross-Process Communication) is a fundamental macOS framework designed to facilitate secure communication between processes while maintaining proper authorization boundaries. The flaw manifests in the listener:shouldAcceptNewConnection method implementation, which serves as the primary authorization checkpoint for incoming connection requests to the XPC service. This method is responsible for determining whether a connecting process should be granted access to the service's functionality, yet it fails to perform any meaningful client authorization checks.
The technical nature of this vulnerability stems from the absence of proper access control mechanisms within the XPC service's connection acceptance logic. When a local process attempts to connect to the XPC service, the shouldAcceptNewConnection method is invoked to evaluate the legitimacy of the connection request. In this case, the method unconditionally returns a positive authorization status regardless of the connecting process's privileges or identity, effectively creating an open door for any local process to establish communication with the service. This represents a classic failure in the principle of least privilege, where the service grants access to all potential clients without proper verification of their credentials or authorization status. The vulnerability directly maps to CWE-284, which addresses improper access control, and specifically relates to the weakness of insufficient authorization checks within process communication frameworks.
The operational impact of this vulnerability is significant for macOS users running affected versions of Fantastical. Any local, unprivileged process on the system can exploit this weakness to establish unauthorized connections to the XPC service and access its methods. This creates a potential attack surface where malicious software or compromised applications could leverage the vulnerability to perform unauthorized operations through Fantastical's service interface. Attackers could potentially manipulate calendar data, access sensitive scheduling information, or execute arbitrary commands through the service's exposed methods. The vulnerability particularly concerns the confidentiality and integrity of user calendar data, as unauthorized processes could read, modify, or delete calendar entries without proper user consent or system authorization. Additionally, this issue could enable privilege escalation scenarios where local attackers could leverage the service access to perform actions that would normally require elevated privileges.
The resolution implemented in version 4.0.16 addresses this vulnerability by properly implementing authorization checks within the XPC service's connection acceptance logic. The fix likely involves modifying the listener:shouldAcceptNewConnection method to verify the connecting process's identity, privileges, and authorization status before granting access to the service. This implementation aligns with the ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation," as it prevents unauthorized processes from gaining access to privileged service interfaces. The update demonstrates proper secure coding practices that should be implemented across all XPC services and inter-process communication frameworks. Organizations should prioritize updating to version 4.0.16 or later to remediate this vulnerability and ensure that their calendar management applications maintain proper access control boundaries. Security practitioners should also consider monitoring for any anomalous XPC service connections or unauthorized access patterns that might indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of implementing proper authorization checks in all inter-process communication mechanisms, particularly those that provide access to sensitive user data or system functionality.