SEC Consult Vulnerability Lab Security Advisory < 20230516-0 >  
title: Multiple Vulnerabilities  
product: Serenity and StartSharp Software  
vulnerable version: < 6.7.1  
fixed version: 6.7.1 or higher  
CVE number: CVE-2023-31285, CVE-2023-31286, CVE-2023-31287  
impact: high  
found: 2023-02-28  
by: Fabian Densborn (Office Vienna)  
SEC Consult Vulnerability Lab  
An integrated part of SEC Consult.  
SEC Consult is part of Eviden, an Atos business  
Europe | Asia | North America  
Vendor description:  
Serenity Software is a software vendor that distributes the Serenity Platform.  
"Serenity is an ASP.NET Core / TypeScript application platform designed to  
simplify and shorten development of data-centric business applications with  
a service based architecture."  
Business recommendation:  
SEC Consult recommends Serenity users to install the latest update and review  
the vendor's changelog for further information.  
Furthermore, an in-depth security analysis performed by security professionals  
is highly advised, as the software may be affected from other security issues.  
Vulnerability overview/description:  
1) Arbitrary File Upload to Stored Cross-Site Scripting (XSS) (CVE-2023-31285)  
The application allows users to upload profile pictures for users.  
It was identified that an attacker has the possibility to upload  
arbitrary malicious files. Although some specific file endings are  
not allowed, it is still possible to upload files without an extension.  
It was possible to:  
โ€ข Upload malicious HTML files that will infect the user's browser with malicious  
JavaScript. As a result, the user's DOM is fully compromised.  
โ€ข Upload malware that will infect the user's operating system upon download and  
local execution.  
Although the option for uploading new profile pictures is only visible to power users,  
users with lower privileges can still trigger the upload functionality.  
2) User Enumeration (CVE-2023-31286)  
It is possible to collect valid email addresses by interacting with the  
"forgot password" function of the application. This vulnerability is  
useful to increase the efficiency of brute-force attacks. If the email  
address is known, it is easier to find the corresponding password.  
3) Reusable Password Reset Tokens (CVE-2023-31287)  
The web application provides the possibility to reset the password via  
email. The corresponding email contains a password reset link which includes  
a user-specific token. When visiting the link, the user can set a new  
password for this account. After changing the password, the password reset link  
remains valid (3 hours) and can be used a second time to change the password  
of the user.  
Proof of concept:  
1) Arbitrary File Upload to Stored Cross-Site Scripting (XSS) (CVE-2023-31285)  
A user can upload arbitrary files to the server, but some file extensions  
like .aspx are not allowed. Nevertheless, malicious files like Word documents  
with enabled macros or other executable malware can be uploaded. There also  
seems to be no anti-virus scan enabled for these files, as it is possible to  
upload the EICAR test file which is flagged as malicious by all antivirus  
Additionally, it is also possible to attack a privileged power user, by  
generating a malicious HTML page, that on visit escalates the role of the  
attacker user. This is possible, because the file is uploaded to the same  
domain and therefore the containing JavaScript executes in the same context as  
the application. The impact of this vulnerability is therefore equal to that  
of a stored XSS vulnerability.  
To upload a malicious HTML file an authenticated user without the role of a  
power user can send the following request:  
POST /File/TemporaryUpload HTTP/2  
Cookie: [...]  
Content-Type: multipart/form-data; boundary=--boundary  
Content-Disposition: form-data; name="Serenity_ImageUploadEditor31[]"; filename="test.html"  
Content-Type: image/png  
<h1>SEC Consult</h1>  
The response reveals the path of the uploaded file:  
HTTP/2 200 OK  
Server: nginx/1.18.0 (Ubuntu)  
Content-Type: application/json  
The uploaded file can then be found under /upload/temporary/f3c960aca7724409a3c4c6e597ce5b92.html.  
The final link will look benign thus it is possible to attack administrator  
users and escalate the privileges of the own user.  
2) User Enumeration (CVE-2023-31286)  
The "forgot password" page lets users request a new password reset mail.  
They need to enter their email address which corresponds to their account  
and receive a mail containing a link to reset their password. Unfortunately,  
the response of this request leaks if a user with the provided email address  
exists or not. If an attacker wants to check if a user account with a  
specific email exists, he can send the following request:  
POST /Account/ForgotPassword HTTP/2  
Content-Type: application/json  
If the user with this mail does not exist, the response will look like this:  
HTTP/2 400 Bad Request  
Server: nginx/1.18.0 (Ubuntu)  
Content-Type: application/json  
"Error": {  
"Message":"Can't find a user with that e-mail adress!"  
If the user with this mail address does exist, the response will look like  
HTTP/2 200 OK  
Server: nginx/1.18.0 (Ubuntu)  
Content-Type: application/json  
3) Reusable Password Reset Tokens (CVE-2023-31287)  
When resetting the password via the "forgot password" functionality on the  
login screen, an email containing a password reset link is sent to the user.  
When clicking on this link, a user can choose a new password for his account.  
However, after changing the password to a new one, the password reset link  
remains valid. It can be used a second time to update the user's password  
although it was already changed. If an attacker gets access to the browser  
history of the user, he can change the password of the user's account and  
access it afterwards.  
Vulnerable / tested versions:  
The following versions are affected:  
< 6.7.0  
Vendor contact timeline:  
2023-04-05: Contacting vendor through  
2023-04-05: Vendor responds to send advisory to  
2023-04-05: Advisory sent to vendor.  
2023-04-06: Vendor released fixes for all three vulnerabilities,  
file upload vulnerability was not fixed properly though.  
2023-04-07: SEC Consult informs vendor about not properly fixed file upload.  
2023-04-07: Vendor released proper fix for file upload vulnerability in v6.7.1.  
2023-04-27: CVE numbers assigned.  
2023-05-16: Public release of security advisory.  
The vendor provides a patch v6.7.1 which includes the fixes for the identified  
security issues.  
The new version can be downloaded here:  
The vendor explicitly notes the following in the changelog:  
"Serene/StartSharp users must either create a new project from the 6.7.0+ template  
or manually apply the relevant changes from this commit to their existing  
applications after updating Serenity packages to 6.7.0+"  
Advisory URL:  
SEC Consult Vulnerability Lab  
SEC Consult is part of Eviden, an Atos business  
Europe | Asia | North America  
About SEC Consult Vulnerability Lab  
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EOF Fabian Densborn / @2023