CVE-2017-5677 in HTML_AJAX
Summary
by MITRE
PEAR HTML_AJAX 0.3.0 through 0.5.7 has a PHP Object Injection Vulnerability in the PHP Serializer. It allows remote code execution. In one viewpoint, the root cause is an incorrect regular expression.
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Analysis
by VulDB Data Team • 11/11/2022
The CVE-2017-5677 vulnerability represents a critical PHP object injection flaw within the PEAR HTML_AJAX library version 0.3.0 through 0.5.7, presenting a significant security risk that can lead to remote code execution. This vulnerability specifically affects the PHP serializer component of the library, which is responsible for handling data serialization and deserialization processes. The flaw occurs when the library improperly processes serialized data, creating an avenue for malicious actors to inject arbitrary PHP objects into the application's execution context. The vulnerability stems from a fundamental issue in how the library handles regular expressions during the deserialization process, allowing attackers to manipulate the parsing logic and inject malicious objects that can be executed as PHP code. This type of vulnerability falls under CWE-502 which specifically addresses Deserialization of Untrusted Data, a category that includes PHP object injection attacks where attackers can manipulate serialized objects to execute arbitrary code.
The operational impact of this vulnerability is severe as it enables remote attackers to execute arbitrary code on affected systems without requiring authentication or privileged access. An attacker can craft malicious serialized data that, when processed by the vulnerable PEAR HTML_AJAX library, will deserialize and execute PHP objects with elevated privileges. This capability allows for complete system compromise, data exfiltration, and the potential for further lateral movement within network environments. The vulnerability affects web applications that utilize the PEAR HTML_AJAX library for AJAX functionality, making it particularly dangerous in environments where web applications are exposed to untrusted input. The attack vector typically involves sending crafted serialized data through HTTP parameters or request bodies that are then processed by the vulnerable library. This attack pattern aligns with ATT&CK technique T1059.007 which covers Scripting and T1203 which involves Exploitation for Client Execution, demonstrating how this vulnerability can be leveraged to achieve code execution on target systems.
Mitigation strategies for CVE-2017-5677 require immediate action to address the root cause through proper input validation and secure deserialization practices. Organizations should upgrade to a patched version of the PEAR HTML_AJAX library that addresses the regular expression handling issue and prevents object injection attacks. The recommended approach includes implementing strict input validation for all serialized data, avoiding direct deserialization of user-supplied input, and employing whitelisting mechanisms to restrict which object types can be deserialized. Security measures should also include monitoring for suspicious serialized data patterns and implementing proper access controls to limit the impact of potential exploitation attempts. Additionally, organizations should consider implementing web application firewalls that can detect and block malicious serialization patterns, as well as conducting comprehensive code reviews to identify similar vulnerabilities in other components of the application stack. The vulnerability demonstrates the importance of secure coding practices and proper validation of serialized data, reinforcing the need for defense-in-depth strategies that include both application-level protections and network-level monitoring to prevent exploitation of similar deserialization vulnerabilities.