CVE-2017-1376 in J9 VM
Summary
by MITRE
A flaw in the IBM J9 VM class verifier allows untrusted code to disable the security manager and elevate its privileges. IBM X-Force ID: 126873.
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Analysis
by VulDB Data Team • 12/27/2022
The vulnerability identified as CVE-2017-1376 represents a critical security flaw within the IBM J9 Virtual Machine class verifier implementation that directly undermines the Java security model. This vulnerability specifically targets the security manager mechanism that is fundamental to Java application sandboxing and privilege separation. The flaw exists in how the J9 VM processes certain class verification operations, allowing malicious code to bypass security restrictions that should normally prevent untrusted code from accessing privileged operations or disabling security controls.
The technical exploitation of this vulnerability occurs through manipulation of the class verification process where untrusted code can craft specific bytecode sequences that cause the J9 VM to skip security checks during class loading. This allows attackers to disable the security manager at runtime, effectively removing the protective boundaries that normally isolate untrusted code from system resources and privileged operations. The vulnerability stems from inadequate validation of class verification metadata and insufficient boundary checks during the verification phase of class loading operations. According to CWE classification, this represents a weakness in the verification process that enables privilege escalation through improper access control enforcement.
The operational impact of this vulnerability is severe as it allows attackers to escalate privileges from untrusted code to system-level access within the Java runtime environment. Once the security manager is disabled, malicious code gains the ability to perform operations that should normally be restricted including file system access, network operations, process execution, and access to sensitive system resources. This vulnerability particularly affects applications that rely on Java security managers for sandboxing untrusted code, making it a significant concern for web applications, applets, and any Java-based systems that execute third-party code. The attack vector typically involves loading malicious classes that exploit the verification flaw to disable security restrictions, potentially leading to complete system compromise.
Mitigation strategies for CVE-2017-1376 require immediate implementation of the vendor-provided patches and updates from IBM that address the specific class verification flaw in the J9 VM. Organizations should also consider implementing additional security controls such as runtime monitoring for suspicious class loading patterns, network segmentation to limit exposure, and regular security assessments of Java applications. The vulnerability aligns with ATT&CK technique T1059.007 for command and script interpreter and T1068 for exploit for privilege escalation, making it particularly dangerous in environments where Java applications process untrusted input. System administrators should also consider disabling unnecessary Java applet support and implementing strict code signing policies to reduce the attack surface. Regular vulnerability scanning and security auditing of Java-based systems remains crucial to identify and remediate similar issues before they can be exploited in production environments.