CVE-2023-33546 in janino
Summary
by MITRE • 06/01/2023
Janino 3.1.9 and earlier are subject to denial of service (DOS) attacks when using the expression evaluator.guess parameter name method. If the parser runs on user-supplied input, an attacker could supply content that causes the parser to crash due to a stack overflow. NOTE: this is disputed by multiple parties because Janino is not intended for use with untrusted input.
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Analysis
by VulDB Data Team • 06/06/2024
The vulnerability identified as CVE-2023-33546 affects Janino versions 3.1.9 and earlier, specifically within the expression evaluator component that handles the guess parameter name method. This issue represents a denial of service condition that can be exploited through stack overflow attacks when the parser processes user-supplied input. The vulnerability stems from inadequate input validation and error handling mechanisms within the Janino expression evaluation engine, which is designed to compile and execute Java expressions at runtime. When malicious input is provided to the parser, particularly through the guess parameter name functionality, the recursive parsing operations can exhaust the available stack memory, leading to application crashes and service disruption.
The technical flaw manifests in the parser's recursive descent parsing algorithm which lacks proper stack depth limitations or input sanitization measures. This vulnerability aligns with CWE-674, which describes "Uncontrolled Recursion" as a weakness where a recursive function lacks proper termination conditions or depth limits, allowing attackers to consume excessive system resources. The stack overflow occurs because the parser's recursive methods do not implement safeguards against deeply nested or malformed input structures that would cause the call stack to grow beyond acceptable limits. The vulnerability is particularly concerning in environments where Janino is used to process untrusted input, such as web applications or API endpoints that accept dynamic expression evaluation requests.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability and stability. When exploited, the denial of service attack can cause the affected application to become unresponsive or crash entirely, requiring manual intervention and system restarts. This is particularly problematic in production environments where continuous availability is critical, as the attack can be executed with minimal resources and technical expertise. The vulnerability affects any system utilizing Janino's expression evaluation capabilities in scenarios involving user input, including web applications, middleware components, and embedded systems that rely on dynamic Java expression compilation. Security professionals should note that while the vendor disputes the severity due to Janino's intended use with trusted input, the vulnerability remains a legitimate concern in real-world deployment scenarios where input validation may be insufficient.
Mitigation strategies should focus on implementing proper input validation and sanitization measures before any user-supplied content reaches the Janino parser. Organizations should consider upgrading to Janino versions beyond 3.1.9 where appropriate, though the vulnerability's disputed nature suggests the primary mitigation lies in deployment practices rather than software patches. System administrators should implement rate limiting and resource monitoring to detect unusual parsing behavior that might indicate exploitation attempts. Additionally, the use of sandboxing techniques and memory limit enforcement can help contain potential stack overflow conditions. According to ATT&CK framework technique T1499.004, this vulnerability could be exploited as part of a denial of service attack, making it relevant to the adversary's capability to disrupt services. Organizations should also consider implementing network segmentation and access controls to limit exposure of systems running Janino to untrusted input sources, while maintaining regular security assessments to identify similar vulnerabilities in other expression evaluation libraries.