CVE-2016-9606 in JBoss Enterprise Application Platform
Summary
by MITRE
JBoss RESTEasy before version 3.1.2 could be forced into parsing a request with YamlProvider, resulting in unmarshalling of potentially untrusted data which could allow an attacker to execute arbitrary code with RESTEasy application permissions.
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Analysis
by VulDB Data Team • 12/25/2020
The vulnerability identified as CVE-2016-9606 affects JBoss RESTEasy versions prior to 3.1.2, presenting a critical security risk through improper handling of YAML data processing within the framework. This flaw exists within the YamlProvider component that is responsible for parsing and unmarshalling YAML content in RESTEasy applications. The vulnerability stems from the framework's inability to properly validate and sanitize YAML input before processing, creating a pathway for malicious actors to exploit the deserialization mechanism. The issue is particularly dangerous because it allows attackers to craft specially formatted YAML payloads that, when processed by the vulnerable RESTEasy application, can trigger arbitrary code execution within the application's security context. This represents a classic deserialization vulnerability where untrusted input is transformed into executable code without proper security boundaries.
The technical implementation of this vulnerability involves the YamlProvider's reliance on Java's object deserialization capabilities when processing YAML content. When RESTEasy encounters YAML data, it attempts to automatically convert the structured data into Java objects through reflection-based mechanisms. The flaw occurs because the framework does not adequately restrict the types of objects that can be instantiated during this deserialization process. Attackers can craft YAML payloads containing references to malicious classes or methods that, when unmarshalled, execute arbitrary code on the target system. This vulnerability aligns with CWE-502 which specifically addresses deserialization of untrusted data and is categorized under the broader ATT&CK technique T1203 for Exploitation for Client Execution. The vulnerability essentially bypasses normal input validation mechanisms by leveraging the legitimate YAML parsing functionality to execute malicious payloads through the application's own deserialization infrastructure.
The operational impact of CVE-2016-9606 extends far beyond simple code execution, as it provides attackers with full control over the affected RESTEasy application and potentially the underlying system. Since the execution occurs with the application's permissions, attackers can access sensitive data, modify application behavior, perform unauthorized operations, and potentially escalate privileges within the system. The vulnerability is particularly concerning in enterprise environments where RESTEasy applications often handle sensitive business data and may be exposed to untrusted inputs from external sources. Organizations running vulnerable versions of RESTEasy are at risk of data breaches, service disruption, and potential lateral movement within their network infrastructure. The attack surface is broad as any RESTEasy application that accepts YAML input through HTTP requests, file uploads, or API endpoints could be compromised, making this vulnerability particularly dangerous for web applications that process external data.
Mitigation strategies for CVE-2016-9606 primarily focus on upgrading to RESTEasy version 3.1.2 or later, which includes proper input validation and restricted deserialization mechanisms. Organizations should also implement network-level controls such as firewalls and API gateways to restrict access to endpoints that process YAML data. Additionally, application-level security measures should include disabling YAML processing where possible, implementing strict input validation, and using whitelisting approaches for allowed object types during deserialization. Security teams should conduct comprehensive vulnerability assessments to identify all instances of affected RESTEasy versions within their infrastructure and establish monitoring procedures to detect potential exploitation attempts. The remediation process should also include reviewing application code to ensure that YAML parsing is not inadvertently enabled in configurations or that appropriate security boundaries are maintained around deserialization operations. Organizations should consider implementing runtime application self-protection (RASP) solutions or similar technologies that can detect and prevent malicious deserialization attempts in real-time, providing defense-in-depth protection against similar vulnerabilities.