November 5, 2020

GHSL-2020-151: Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) in little-aspnetcore-todo

Jaroslav Lobačevski

Summary

little-aspnetcore-todo is vulnerable to Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) that may lead to the elevation of privileges and per-user denial of service (DoS).

Product

little-aspnetcore-todo

Tested Version

Master branch.

Details

Issue 1: XSS (CVE-2018-0784)

The application doesn't have a fix for CVE-2018-0784 that was found in ASP.NET Core templates. It is vulnerable to XSS if the logged-in user is tricked into clicking a malicious link like https://localhost:44315/manage/EnableAuthenticator?AuthenticatorUri=%22%3E%3C/div%3E%00%00%00%00%00%00%00%3Cscript%3Ealert(%22XSS%22)%3C/script%3E and enters an invalid verification code. More details are available in this blog post.

Impact

This issue may lead to the elevation of privileges.

Remediation

Modify the code according to the instructions from the ASP.NET advisory.

Issue 2: CSRF (CVE-2018-0785)

The application doesn't have a fix for CVE-2018-0785 that was found in ASP.NET Core templates. It is vulnerable to CSRF. A logged-in user with enabled Second Factor Authentication (2FA) may lose their recovery codes if they are tricked into clicking a link like https://localhost:44315/manage/GenerateRecoveryCodes or visit a malicious site that makes the request without the user's consent. As a result the user may be permanently locked out of their account after losing access to their 2FA device, as the initial recovery codes would no longer be valid.

Impact

This issue may lead to a per-user DoS.

Remediation

Modify the code according to the instructions from the ASP.NET advisory.

Coordinated Disclosure Timeline

Credit

This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).

Contact

You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2020-151 in any communication regarding this issue.