CVE-2019-13376 in phpBB
Summary
by MITRE
phpBB version 3.2.7 allows the stealing of an Administration Control Panel session id by leveraging CSRF in the Remote Avatar feature. The CSRF Token Hijacking leads to stored XSS
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Analysis
by VulDB Data Team • 09/10/2020
The vulnerability identified as CVE-2019-13376 represents a critical security flaw in phpBB version 3.2.7 that exploits cross-site request forgery mechanisms to compromise administrative sessions. This vulnerability specifically targets the Remote Avatar feature within the phpBB forum software, creating a pathway for attackers to hijack administrative control panel sessions through maliciously crafted requests that leverage CSRF token manipulation. The flaw stems from insufficient validation of CSRF tokens when processing avatar requests, allowing unauthorized users to execute administrative actions on behalf of legitimate administrators. This represents a significant escalation of privileges vulnerability that directly impacts the security posture of phpBB installations.
The technical implementation of this vulnerability involves the exploitation of a CSRF token hijacking mechanism that occurs during the processing of remote avatar requests within the administrative control panel. When administrators access the avatar management functionality, the system fails to properly validate that the CSRF token originates from a legitimate administrative session. This weakness allows attackers to craft malicious requests that appear to come from authenticated administrators, effectively stealing their session identifiers and gaining unauthorized access to administrative functions. The vulnerability specifically affects the Remote Avatar feature which allows administrators to set avatars from external URLs, creating a vector for session hijacking that bypasses normal authentication mechanisms.
The operational impact of CVE-2019-13376 extends beyond simple session theft to encompass full administrative control over affected phpBB installations. Successful exploitation enables attackers to modify forum configurations, delete or manipulate user accounts, alter forum content, and potentially exfiltrate sensitive data from the administrative control panel. The stored XSS component of this vulnerability further amplifies the risk by allowing attackers to inject malicious scripts that can persist across user sessions and potentially compromise additional users within the forum environment. This vulnerability directly maps to CWE-352, which defines Cross-Site Request Forgery, and aligns with ATT&CK technique T1078.004 for Valid Accounts, as it leverages legitimate administrative credentials through session hijacking rather than brute force attacks.
Security mitigations for CVE-2019-13376 require immediate implementation of phpBB version 3.2.8 or later, which includes patches addressing the CSRF token validation issues in the Remote Avatar feature. Organizations should also implement additional defensive measures including monitoring for unusual administrative activity, implementing network segmentation to limit access to administrative interfaces, and ensuring that all users access the forum through secure connections. The patch addresses the root cause by strengthening CSRF token validation and ensuring that administrative actions require proper authentication verification regardless of the avatar source. Security teams should also conduct comprehensive vulnerability assessments to identify any potential exploitation attempts and implement intrusion detection systems to monitor for suspicious administrative requests. The vulnerability highlights the importance of proper session management and CSRF protection in web applications, particularly in administrative interfaces where elevated privileges can lead to complete system compromise.