===================================================================== CERT-Renater Note d'Information No. 2022/VULN398 _____________________________________________________________________ DATE : 25/10/2022 HARDWARE PLATFORM(S): / OPERATING SYSTEM(S): Systems running getkirby/cms (Composer) versions prior to 3.5.8.2, 3.6.6.2, 3.7.5.1, 3.8.1. ===================================================================== https://github.com/getkirby/kirby/security/advisories/GHSA-43qq-qw4x-28f8 https://github.com/getkirby/kirby/security/advisories/GHSA-c27j-76xg-6x4f _____________________________________________________________________ User enumeration in the code-based login and password reset forms Moderate bastianallgeier published GHSA-43qq-qw4x-28f8 Package getkirby/cms (Composer) Affected versions 3.5.0-3.5.8.1, 3.6.0-3.6.6.1, 3.7.0-3.7.5, 3.8.0 Patched versions 3.5.8.2, 3.6.6.2, 3.7.5.1, 3.8.1 Description TL;DR This vulnerability only affects you if you are using the code or password-reset auth method with the auth.methods option. It can only be successfully exploited under server configuration conditions outside of the attacker's control. Introduction User enumeration is a type of vulnerability that allows attackers to confirm which users are registered in a Kirby installation. This information can be abused for social engineering attacks against users of the site or to find out the organizational structure of the company. User enumeration attacks are performed by entering an existing and a non-existing user into the email address field of the login form. If the system returns a different response or behaves differently depending on whether the user exists, the attacker can enter unknown email addresses and use the different behavior as a clue for the (non-)existing user. Impact Under normal circumstances, entering an invalid email address results in a "fake" login code form that looks exactly like the one of an existing user (unless debugging is enabled). However, the code that handles the creation of a code challenge (for code-based login or password reset) didn't catch errors that occurred while the challenge request was processed: If the challenge itself runs into an error (e.g. if the email could not be sent), attackers could tell existing users (where the challenge code is called) from non-existing users (where the challenge code is not called and therefore does not output an error). If you are using the user.login:failed hook and any exception is thrown within the hook, attackers could see that the user does not exist. As long as no error occurs during challenge creation and during the processing of the user.login:failed hook, your Kirby sites are not affected by this vulnerability. Patches The problems have been patched in Kirby 3.5.8.2, Kirby 3.6.6.2, Kirby 3.7.5.1 and Kirby 3.8.1. Please update to one of these or a later version to fix the vulnerability. All of the mentioned releases contain two patches for this vulnerability: All errors that occur during the creation of an auth challenge (code-based login or password reset) are swallowed by the backend and only displayed to the user if debugging is enabled. We added a new auth.debug option that can be enabled separately from the debug option. If disabled, auth errors are only printed to the PHP error log. This ensures that security-critical errors are only displayed if they are really necessary for debugging. Workarounds We recommend to update to one of the patch releases. If you cannot update immediately, you can work around the issue by setting the auth.methods option to password, which disables the code-based login and password reset forms. However please note that your site will still be vulnerable against another user enumeration issue that was also fixed in the same patch releases. Credits Thanks to Florian Merz (@florianmrz) of hatchery.io for responsibly reporting the identified issue. Severity Moderate 4.8/ 10 CVSS base metrics Attack vector Network Attack complexity High Privileges required None User interaction None Scope Unchanged Confidentiality Low Integrity Low Availability None CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N CVE ID CVE-2022-39314 Weaknesses CWE-204 Credits @florianmrz florianmrz _____________________________________________________________________ User enumeration in the brute force protection Moderate bastianallgeier published GHSA-c27j-76xg-6x4f Package getkirby/cms (Composer) Affected versions <=3.5.8.1, 3.6.0-3.6.6.1, 3.7.0-3.7.5, 3.8.0 Patched versions 3.5.8.2, 3.6.6.2, 3.7.5.1, 3.8.1 Description TL;DR This vulnerability affects all Kirby sites with user accounts (unless Kirby's API and Panel are disabled in the config). It can only be exploited for targeted attacks because the attack does not scale to brute force. Introduction User enumeration is a type of vulnerability that allows attackers to confirm which users are registered in a Kirby installation. This information can be abused for social engineering attacks against users of the site or to find out the organizational structure of the company. User enumeration attacks are performed by entering an existing and a non-existing user into the email address field of the login form. If the system returns a different response or behaves differently depending on whether the user exists, the attacker can enter unknown email addresses and use the different behavior as a clue for the (non-)existing user. Impact Kirby comes with a built-in brute force protection. By default, it will prevent further login attempts after 10 failed logins from a single IP address or of a single existing user. After every failed login attempt, Kirby inserts a random delay between one millisecond and two seconds to make automated attacks harder and to avoid leaking whether the user exists. Unfortunately, this random delay was not inserted after the brute force limit was reached. Because Kirby only tracks failed login attempts per email address for existing users but always tracks failed login attempts per IP address, this behavior could be abused by attackers for user enumeration. For this to work, an attacker would need to create login requests beyond the trials limit (which is 10 by default) from two or more IP addresses. After the trials limit was reached, the login form immediately blocked further requests for existing users, but not for invalid users. This exploit does not scale to brute force attacks because of the delay during the first 10 requests per user, the faint difference between the responses for valid and invalid users and the fact that code-based logins would send an email for every login attempt, which makes the attack easy to spot. The vulnerability is therefore only relevant for targeted attacks. Patches The problem has been patched in Kirby 3.5.8.2, Kirby 3.6.6.2, Kirby 3.7.5.1 and Kirby 3.8.1. Please update to one of these or a later version to fix the vulnerability. In all of the mentioned releases, we have rewritten the affected code so that the delay is also inserted after the brute force limit is reached. Severity Moderate 6.5/ 10 CVSS base metrics Attack vector Network Attack complexity Low Privileges required None User interaction None Scope Unchanged Confidentiality Low Integrity Low Availability None CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N CVE ID CVE-2022-39315 Weaknesses CWE-204 ========================================================= + CERT-RENATER | tel : 01-53-94-20-44 + + 23/25 Rue Daviel | fax : 01-53-94-20-41 + + 75013 Paris | email:cert@support.renater.fr + =========================================================