Multiple Vulnerabilities in Serenity and StartSharp Software


Multiple Vulnerabilities


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






Fabian Densborn (Office Vienna) | SEC Consult Vulnerability Lab

Multiple vulnerabilities have been identified in Serenity and StartSharp Software that might allow an attacker to upload arbitrary files and attack users via malicious code, enumerate existing user accounts or re-use password reset tokens.

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:

  • Upload malicious HTML files that will infect the user's browser with malicious  JavaScript. As a result, the user's DOM is fully compromised.
  • Upload malware that will infect the user's operating system upon download and local execution.

Note: 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 software.

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
Origin: https://

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
Origin: https://
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 this:

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


EOF Fabian Densborn / @2023


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