CVE-2022-43687 is a vulnerability affecting Concrete CMS, an open-source content management system formerly known as concrete5. The flaw exists in versions below 8.5.10 and between 9.0.0 and 9.1.2. The core issue is that the system does not issue a new session identifier (session ID) upon successful OAuth authentication. OAuth is a widely used authorization framework that allows users to authenticate via third-party providers. Proper session management, including session ID regeneration after authentication, is critical to prevent session fixation attacks. Without issuing a new session ID, an attacker who can fixate a session ID prior to authentication could hijack the authenticated session, gaining unauthorized access with the victim’s privileges. This vulnerability is classified under CWE-384 (Session Fixation). The CVSS v3.1 base score is 5.4 (medium severity), with vector AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N, indicating that the attack can be performed remotely over the network with low attack complexity, no privileges required, but requires user interaction (the victim to authenticate). The impact is limited to confidentiality and integrity, with no availability impact. There are no known exploits in the wild as of the published date. The recommended remediation is to update Concrete CMS to versions 8.5.10 or 9.1.3 and above, where the session ID regeneration issue has been fixed.

For European organizations using Concrete CMS, this vulnerability poses a risk of session fixation attacks that could lead to unauthorized access to web applications managed by Concrete CMS. This can result in exposure of sensitive content, unauthorized content modification, or privilege escalation within the CMS environment. Sectors such as government, education, media, and enterprises that rely on Concrete CMS for their web presence could face confidentiality breaches and integrity violations. Although the vulnerability does not directly affect availability, the compromise of session integrity can undermine trust and lead to reputational damage. The requirement for user interaction (victim login) somewhat limits the attack vector but does not eliminate risk, especially in phishing or social engineering scenarios common in targeted attacks. Given the widespread use of Concrete CMS in Europe, especially among small and medium-sized organizations that may delay patching, the threat is relevant and should be addressed promptly.

1. Immediate upgrade of Concrete CMS installations to version 8.5.10 or 9.1.3 and later, as these versions include the fix for session ID regeneration post-OAuth authentication. 2. Implement additional session management controls such as setting secure, HttpOnly, and SameSite cookie attributes to reduce session hijacking risks. 3. Monitor authentication logs for unusual session behavior or repeated login attempts that could indicate exploitation attempts. 4. Educate users about phishing and social engineering risks to reduce the chance of attackers leveraging user interaction requirements. 5. If upgrading is not immediately feasible, consider deploying web application firewalls (WAFs) with custom rules to detect and block suspicious session fixation attempts. 6. Conduct regular security assessments and penetration testing focusing on authentication and session management mechanisms. 7. Review OAuth integration configurations to ensure they follow best practices and do not expose additional weaknesses.