CVE-2017-18349 in Fastjson
Summary
by MITRE
parseObject in Fastjson before 1.2.25, as used in FastjsonEngine in Pippo 1.11.0 and other products, allows remote attackers to execute arbitrary code via a crafted JSON request, as demonstrated by a crafted rmi:// URI in the dataSourceName field of HTTP POST data to the Pippo /json URI, which is mishandled in AjaxApplication.java.
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Analysis
by VulDB Data Team • 05/30/2023
The vulnerability identified as CVE-2017-18349 represents a critical remote code execution flaw within the fastjson library ecosystem, specifically affecting versions prior to 1.2.25. This vulnerability manifests through the parseObject method when processing JSON requests, creating a dangerous attack vector that enables remote adversaries to execute arbitrary code on affected systems. The flaw was particularly impactful because it was present in FastjsonEngine implementations within Pippo 1.11.0 and other software products, making it a widespread concern across numerous applications that relied on this popular Java JSON processing library. The vulnerability's exploitation occurs through a crafted JSON request that specifically targets the dataSourceName field within HTTP POST data sent to the Pippo /json URI endpoint, demonstrating how seemingly innocuous JSON parsing operations can become dangerous attack surfaces when proper input validation and sanitization are absent.
The technical implementation of this vulnerability stems from fastjson's deserialization process, which automatically handles object creation from JSON data without adequate security checks. When the parseObject method encounters a crafted rmi:// URI within the dataSourceName field, it triggers the library's automatic deserialization mechanism, causing the system to attempt to establish a remote connection to the specified RMI endpoint. This behavior violates fundamental security principles by allowing untrusted input to drive object instantiation and execution, creating a direct pathway for remote code execution. The vulnerability operates at the core of the library's deserialization logic, where the absence of proper URI validation and protocol restrictions enables attackers to specify malicious RMI endpoints that the library will attempt to connect to and execute code from. This flaw aligns with CWE-502, which describes deserialization of untrusted data as a critical security weakness, and demonstrates how improper input handling can lead to arbitrary code execution through indirect means.
The operational impact of this vulnerability extends far beyond individual applications, as it affects a wide ecosystem of software products that utilize fastjson for JSON processing. Attackers can leverage this vulnerability to execute arbitrary commands on vulnerable systems, potentially leading to complete system compromise, data exfiltration, or further lateral movement within network environments. The attack surface is particularly concerning because it requires minimal privileges to exploit, as the vulnerability exists in the JSON parsing layer that is commonly used for API endpoints and web services. Organizations running affected versions of Pippo or other software that incorporates vulnerable fastjson versions face significant risk of unauthorized access and system compromise, especially when these applications are exposed to untrusted network traffic. The vulnerability's persistence in multiple products means that the attack surface is extensive, potentially affecting hundreds of thousands of systems across various industries and deployment scenarios.
Mitigation strategies for CVE-2017-18349 require immediate action to address the vulnerable fastjson versions, with the primary recommendation being the upgrade to fastjson version 1.2.25 or later, which includes proper input validation and sanitization measures. Organizations should implement network-level restrictions to prevent access to vulnerable endpoints and ensure that all JSON processing operations include proper input validation and sanitization before deserialization occurs. The implementation of secure deserialization practices, such as whitelisting allowed classes and implementing strict protocol validation, can significantly reduce the risk of exploitation. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all systems running affected software versions and implement monitoring solutions to detect potential exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for remote code execution and T1071.004 for application layer protocol usage, highlighting the need for network segmentation and application-level security controls. The vulnerability underscores the importance of maintaining up-to-date libraries and implementing defense-in-depth strategies to protect against similar deserialization vulnerabilities that may exist in other components of the application stack.