CVE-2018-8073 in Yii
Summary
by MITRE
Yii 2.x before 2.0.15 allows remote attackers to execute arbitrary LUA code via a variant of the CVE-2018-7269 attack in conjunction with the Redis extension.
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Analysis
by VulDB Data Team • 01/15/2020
The vulnerability identified as CVE-2018-8073 represents a critical remote code execution flaw affecting the Yii 2 web application framework version 2.0.15 and earlier. This vulnerability specifically targets applications utilizing the Redis extension within the Yii framework, creating a dangerous attack vector that allows remote adversaries to execute arbitrary Lua code on affected systems. The flaw arises from insufficient input validation and sanitization within the Redis caching mechanism, enabling attackers to inject malicious Lua scripts through crafted HTTP requests that are then processed by the Redis server.
The technical exploitation of this vulnerability builds upon the previously discovered CVE-2018-7269 attack pattern, which targeted similar weaknesses in the Redis extension's handling of serialized data. The flaw occurs when the Yii framework's Redis cache component processes user-supplied input without proper validation, allowing malicious payloads to be interpreted as Lua code by the Redis server. This creates a chain of execution where attacker-controlled data flows from the web application layer through the Redis extension into the Redis server itself, where it is interpreted and executed as Lua scripts. The vulnerability is particularly dangerous because it leverages the Redis server's EVAL command functionality, which allows arbitrary Lua script execution, and the Yii framework's caching mechanisms that expose this functionality to external input.
The operational impact of CVE-2018-8073 extends far beyond simple code execution, as it provides attackers with complete control over affected systems. Successful exploitation can lead to full system compromise, data exfiltration, lateral movement within network environments, and potential persistence mechanisms. Organizations running Yii applications with Redis caching enabled are at risk of unauthorized access to sensitive data, application manipulation, and potential use as a foothold for broader network infiltration. The vulnerability affects web applications that utilize Redis for caching, session storage, or other data management functions, making it particularly prevalent in modern web architectures that rely on Redis for performance optimization. According to CWE classification, this vulnerability maps to CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and specifically addresses the execution of arbitrary code through injection attacks.
Mitigation strategies for CVE-2018-8073 primarily focus on upgrading to the patched version of the Yii framework, specifically version 2.0.15 or later, which addresses the input validation issues in the Redis extension. Organizations should also implement network-level restrictions to limit access to Redis servers, ensuring that only trusted application servers can communicate with Redis instances. Additional defensive measures include disabling unnecessary Redis commands, implementing proper input sanitization at multiple layers, and monitoring for suspicious Redis activity patterns. The ATT&CK framework categorizes this vulnerability under T1059.007 for "Command and Scripting Interpreter: Lua" and T1190 for "Exploit Public-Facing Application," highlighting the attack techniques that leverage this flaw. Security teams should also consider implementing web application firewalls to detect and block malicious payloads targeting Redis extension vulnerabilities, and conduct regular security assessments to identify potentially vulnerable applications within their infrastructure.