CVE-2019-16993 in phpBB
Summary
by MITRE
In phpBB before 3.1.7-PL1, includes/acp/acp_bbcodes.php has improper verification of a CSRF token on the BBCode page in the Administration Control Panel. An actual CSRF attack is possible if an attacker also manages to retrieve the session id of a reauthenticated administrator prior to targeting them.
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Analysis
by VulDB Data Team • 12/29/2023
The vulnerability identified as CVE-2019-16993 affects phpBB versions prior to 3.1.7-PL1 and resides within the administration control panel's BBCode management functionality. This issue represents a critical security flaw that undermines the integrity of the web application's administrative interface. The vulnerability specifically impacts the includes/acp/acp_bbcodes.php file where the Cross-Site Request Forgery token validation is insufficiently implemented. This weakness creates a scenario where authenticated administrators can be targeted through automated attacks that exploit the lack of proper token verification mechanisms.
The technical flaw manifests as a failure in the CSRF protection mechanism that should validate the authenticity of administrative actions performed through the web interface. When an administrator accesses the BBCode configuration page within the ACP, the system should verify that the request originates from a legitimate administrative session rather than from an attacker-controlled source. However, due to inadequate validation of the CSRF token, malicious actors can craft requests that appear to come from authenticated administrators. The vulnerability requires an attacker to obtain a valid session identifier from a reauthenticated administrator, which then enables the execution of unauthorized administrative actions. This combination of factors creates a particularly dangerous scenario where session hijacking and CSRF exploitation work together to compromise administrative privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables attackers to perform administrative functions without proper authorization. An attacker who successfully exploits this vulnerability could modify BBCode configurations, potentially introducing malicious code that affects forum content, manipulate user permissions, or alter forum settings. The attack vector becomes more feasible when considering that administrators may be targeted during active sessions, particularly when they are performing routine administrative tasks. This vulnerability directly violates the principle of least privilege and undermines the trust model of the web application's authentication system. The attack requires minimal technical expertise beyond basic web application exploitation techniques and can result in significant damage to forum integrity and user data.
Security professionals should consider this vulnerability in the context of the CWE-352 weakness classification which specifically addresses Cross-Site Request Forgery vulnerabilities. The ATT&CK framework categorizes this as a privilege escalation technique under the "Exploitation for Privilege Escalation" tactic. The vulnerability demonstrates the importance of implementing robust session management and token validation mechanisms in web applications. Organizations using affected phpBB versions should immediately apply the patch released in version 3.1.7-PL1 which addresses the CSRF token verification issue. Additionally, implementing proper session management practices including secure session cookie attributes, regular session regeneration, and monitoring for suspicious administrative activities can help mitigate the risk. Network segmentation and web application firewalls can provide additional layers of defense, though the primary mitigation remains the application of the vendor-provided security patch. The vulnerability highlights the critical need for continuous security assessment and timely patch management in maintaining web application security posture.