CVE-2018-19499 in Vanilla
Summary
by MITRE
Vanilla before 2.5.5 and 2.6.x before 2.6.2 allows Remote Code Execution because authenticated administrators have a reachable call to unserialize in the Gdn_Format class.
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Analysis
by VulDB Data Team • 04/14/2020
The vulnerability identified as CVE-2018-19499 represents a critical remote code execution flaw affecting Vanilla forums versions prior to 2.5.5 and 2.6.x versions before 2.6.2. This vulnerability stems from an insecure deserialization issue within the Gdn_Format class, which is a core component of the Vanilla forum platform. The flaw specifically allows authenticated administrators to trigger remote code execution by leveraging a reachable unserialize call, making it particularly dangerous as it requires only administrative privileges rather than elevated system access. The vulnerability exists in the way the application processes user-supplied data during format conversion operations, creating an attack surface that can be exploited by malicious actors who have gained administrative access to the forum.
The technical exploitation of this vulnerability occurs through the Gdn_Format class's handling of serialized data, which is processed without proper input validation or sanitization. When an authenticated administrator accesses certain endpoints that utilize the unserialize function, the application becomes vulnerable to malicious payload injection. This flaw directly maps to CWE-502, which categorizes insecure deserialization as a serious weakness in software applications, particularly when user-controllable data is passed to unserialize functions. The vulnerability enables attackers to execute arbitrary code on the affected server, potentially leading to complete system compromise, data exfiltration, or further network infiltration. The attack vector is particularly concerning because it leverages legitimate administrative functionality, making detection more difficult and allowing for persistent access within the compromised environment.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with the capability to establish persistent backdoors, escalate privileges, and manipulate forum content. Once exploited, the attacker can gain full control over the Vanilla forum server, potentially using it as a staging point for attacks against other systems within the network. The vulnerability affects the integrity and availability of the forum platform, as malicious actors can modify user data, delete content, or create unauthorized administrative accounts. Organizations running affected versions of Vanilla forums face significant risk of data breaches and service disruption, particularly in environments where administrative credentials might be compromised through phishing or other social engineering attacks. The vulnerability's exploitation can also lead to compliance violations and regulatory penalties, especially in industries with strict data protection requirements.
Mitigation strategies for CVE-2018-19499 primarily focus on immediate patching of affected Vanilla forum versions to the latest secure releases. Organizations should implement strict access controls and monitoring for administrative accounts, ensuring that only trusted personnel have access to administrative functions. The recommended approach includes disabling or restricting the use of unserialize functions in application code, implementing proper input validation for all user-supplied data, and conducting regular security audits of application components. Additionally, network segmentation and intrusion detection systems should be deployed to monitor for suspicious activities related to forum administration functions. Organizations should also consider implementing application whitelisting policies to prevent execution of unauthorized code and establish incident response procedures to quickly address potential exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.007 for command and script injection highlights the importance of comprehensive security controls that address multiple attack vectors. Regular security training for administrators and implementation of principle of least privilege access controls can significantly reduce the risk of successful exploitation, as the vulnerability requires administrative credentials to be effective.