Advisory ID: SYSS-2021-048  
Product: PHP Event Calendar  
Manufacturer: Kayson Group Ltd.  
Affected Version(s): PHP Event Calendar Lite edition  
Tested Version(s): PHP Event Calendar Lite edition  
Vulnerability Type: SQL injection (CWE-89)  
Risk Level: High  
Solution Status: Closed  
Manufacturer Notification: 2021-08-09  
Solution Date: 2021-09-03  
Public Disclosure: 2021-11-04  
CVE Reference: CVE-2021-42077  
Authors of Advisory: Erik Steltzner, SySS GmbH  
Maurizio Ruchay, SySS GmbH  
PHP Event Calendar is a multi-user web application designed  
to manage and publish calendar events.  
The manufacturer describes the product as follows (see [1] and [2]):  
"PHP Event Calendar features day, week, month, year, agenda, and  
resource views. It includes built-in reminder support so you can  
deliver full-featured event scheduling management systems in  
the shortest possible time."  
"PHP Event Calendar is a out-of-box web calendar/scheduler solution.  
It will run on web servers that support PHP 5.3 and higher."  
Vulnerability Details:  
Due to improper validation, the application is vulnerable to SQL injection  
attacks. For example, the following SQL statement can be used as a  
username during the login process to bypass the authentication:  
' OR '1' = '1' #  
This vulnerability cannot only be exploited to bypass the login.  
It can also be used to execute SQL statements directly on the database,  
allowing an adversary in some cases to completely compromise the  
database system.  
Proof of Concept (PoC):  
The following request shows how it is possible for an adversary to bypass  
the login mask with the SQL statement "' OR '1' = '1' #":  
POST /server/ajax/user_manager.php HTTP/1.1  
Host: <rhost>  
HTTP/1.1 200 OK  
Cookie: PHPSESSID=xxxxxxxxxxxxxxxxxxxxxxxxxx  
Connection: close  
success#Welcome ' OR '1' = '1' #  
The web application accepts the request and the adversary is now logged  
in into the app with admin privileges.  
Update to a recent version of PHP Event Calendar.  
Disclosure Timeline:  
2021-07-29: Vulnerability discovered  
2021-08-09: Vulnerability reported to manufacturer  
2021-09-03: Patch released by manufacturer  
2021-11-04: Public disclosure of vulnerability  
[1] Product Website for PHP Event Calendar  
[2] Documentation Website for PHP Event Calendar  
[3] SySS Security Advisory SYSS-2021-048  
[4] SySS Responsible Disclosure Policy  
[5] PHP Prepared Statements:  
This security vulnerability was found by Erik Steltzner and  
Maurizio Ruchay of SySS GmbH.  
Public Key:  
Key ID: 0x4C7979CE53163268  
Key Fingerprint: 6538 8216 555B FBE7 1E01 7FBD 4C79 79CE 5316 3268  
Public Key:  
Key ID: 0xC7D20E267F0FA978  
Key Fingerprint: D506 AB5A FE3E 09AE FFBE DEB2 C7D2 0E26 7F0F A978  
The information provided in this security advisory is provided "as is"  
and without warranty of any kind. Details of this security advisory may  
be updated in order to provide as accurate information as possible. The  
latest version of this security advisory is available on the SySS website.  
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