CVE-2021-37597 in WP Cerber
Summary
by MITRE • 08/20/2021
WP Cerber before 8.9.3 allows MFA bypass via wordpress_logged_in_[hash] manipulation.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/25/2021
The vulnerability CVE-2021-37597 affects WP Cerber security plugin versions prior to 8.9.3, representing a critical authentication bypass flaw that undermines multi-factor authentication protections. This vulnerability specifically targets the wordpress_logged_in_[hash] cookie manipulation mechanism, which is designed to maintain user sessions and enforce additional security layers. The flaw allows attackers to circumvent the multi-factor authentication requirements by manipulating session cookies, effectively granting unauthorized access to protected WordPress administrative interfaces.
The technical implementation of this vulnerability stems from improper validation of authentication tokens within the WP Cerber plugin's session management system. When users authenticate with multi-factor authentication enabled, the system should verify both the primary credentials and the secondary authentication factor before establishing a persistent session. However, the vulnerable version fails to adequately validate the wordpress_logged_in_[hash] cookie contents, allowing malicious actors to craft or modify these cookies to bypass the MFA verification process. This type of vulnerability aligns with CWE-287, which addresses improper authentication mechanisms, and represents a classic session management weakness that has been documented across numerous web applications.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally compromises the security posture of WordPress installations relying on WP Cerber for protection. Attackers can exploit this flaw to gain administrative privileges without providing valid second-factor authentication, potentially leading to complete system compromise including data exfiltration, malware deployment, and unauthorized modifications to website content. The vulnerability affects organizations that depend on multi-factor authentication as a primary security control, rendering their protection mechanisms ineffective against this specific attack vector.
Mitigation strategies for CVE-2021-37597 require immediate patching of the WP Cerber plugin to version 8.9.3 or later, which contains the necessary fixes for the session validation logic. Organizations should also implement additional security measures including monitoring for suspicious cookie manipulation patterns, implementing web application firewalls with custom rules to detect and block malicious cookie modifications, and conducting regular security audits of authentication mechanisms. The ATT&CK framework categorizes this vulnerability under T1110.003 - Brute Force: Password Guessing, as attackers can leverage this bypass to avoid traditional password cracking methods. Additionally, organizations should consider implementing additional authentication layers such as IP whitelisting, enhanced logging, and regular security assessments to reduce the attack surface and prevent exploitation of similar session management weaknesses.