alextselegidis easyappointments up to 1.5.x Google OAuth Google.php provider_id improper synchronization

Summaryinfo

A vulnerability was found in alextselegidis easyappointments up to 1.5.x. It has been declared as critical. This affects an unknown function of the file application/controllers/Google.php of the component Google OAuth Handler. The manipulation of the argument provider_id results in improper synchronization. This vulnerability is reported as CVE-2026-52841. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical has been found in alextselegidis easyappointments up to 1.5.x. Affected is some unknown processing of the file application/controllers/Google.php of the component Google OAuth Handler. The manipulation of the argument provider_id with an unknown input leads to a improper synchronization vulnerability. CWE is classifying the issue as CWE-662. The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Easy!Appointments is a self hosted appointment scheduler. In versions prior to 1.6.0, `Google::oauth` at `application/controllers/Google.php:278` stores its URL-supplied `provider_id` in the session, and `oauth_callback` saves the issued Google OAuth token against that row without checking the caller owns the provider. Any logged-in backend user (admin, provider, or secretary) rebinds a peer provider's Google sync to a Google account they control. The peer's appointments then sync into the attacker's calendar with each customer's name and email attached as attendee data. Version 1.6.0 patches the issue.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-52841 since 06/08/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit.

By approaching the search of inurl:application/controllers/Google.php it is possible to find vulnerable targets with Google Hacking.

Upgrading to version 1.6.0 eliminates this vulnerability.

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Productinfo

Type

• Appointment Software

Vendor

• alextselegidis

Name

• easyappointments

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5

Website

• Product: https://github.com/alextselegidis/easyappointments/

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