CVE-2021-2432: Oracle JDK JNDI Component DOS Vulnerability

CVE-2021-2432 Overview

CVE-2021-2432 is a vulnerability in the Java SE product of Oracle Java SE, specifically affecting the JNDI (Java Naming and Directory Interface) component. The supported version that is affected is Java SE: 7u301. This difficult-to-exploit vulnerability allows an unauthenticated attacker with network access via multiple protocols to compromise Java SE, potentially resulting in unauthorized ability to cause a partial denial of service (partial DOS) of Java SE.

This vulnerability applies to Java deployments, typically in clients running sandboxed Java Web Start applications or sandboxed Java applets, that load and run untrusted code (e.g., code that comes from the internet) and rely on the Java sandbox for security. The vulnerability can also be exploited by using APIs in the JNDI component, for example, through a web service which supplies data to the APIs.

Critical Impact

Successful exploitation can cause partial denial of service affecting Java SE availability. Organizations running Java SE 7u301 in client environments with untrusted code execution or exposed web services should assess their risk exposure.

Affected Products

• Oracle JDK 1.7.0 Update 301
• McAfee ePolicy Orchestrator (versions prior to 5.10.0 Update 11)
• McAfee ePolicy Orchestrator 5.10.0 through Update 10

Discovery Timeline

• July 21, 2021 - CVE-2021-2432 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2021-2432

Vulnerability Analysis

The vulnerability resides in the JNDI component of Oracle Java SE 7u301. JNDI provides a unified interface for Java applications to interact with various naming and directory services such as LDAP, DNS, and RMI registries. The flaw allows an unauthenticated attacker to send specially crafted requests over the network that can disrupt the normal operation of the JNDI component.

The attack complexity is high, meaning successful exploitation requires specific conditions to be met, reducing the likelihood of widespread attacks. However, no privileges or user interaction are required to initiate an attack, making it accessible to remote attackers who can reach vulnerable systems over the network.

Root Cause

While specific technical details have not been disclosed by Oracle (categorized as NVD-CWE-noinfo), the vulnerability appears to be related to improper handling of certain inputs within the JNDI component. The JNDI subsystem's processing of network-supplied data contains a flaw that can be triggered to cause service disruption. The vulnerability's availability-only impact suggests a resource exhaustion or exception handling issue rather than memory corruption.

Attack Vector

The attack vector is network-based, allowing exploitation through multiple protocols supported by JNDI. Attackers can target:

1. Client-side attacks: Malicious code embedded in Java Web Start applications or Java applets that execute within the sandbox can trigger the vulnerability when the client processes untrusted content from the internet.

2. Server-side attacks: Web services or APIs that utilize the JNDI component and accept external input can be targeted by supplying malicious data that triggers the vulnerability.

The attack complexity is classified as high, indicating that exploitation requires specific circumstances such as particular network configurations, timing conditions, or the presence of specific application behaviors. Due to the absence of verified proof-of-concept code for this vulnerability, technical details on specific exploitation techniques remain limited. Refer to the Oracle CPU July 2021 Alert for authoritative guidance.

Detection Methods for CVE-2021-2432

Indicators of Compromise

• Unusual JNDI lookup failures or exceptions in Java application logs
• Increased frequency of partial service outages affecting Java-based applications
• Abnormal network traffic patterns targeting Java application ports with malformed JNDI requests
• Application performance degradation or intermittent unavailability in Java SE 7u301 environments

Detection Strategies

• Implement network monitoring to identify anomalous traffic patterns directed at Java applications using JNDI services
• Configure Java application logging to capture detailed JNDI operation errors and exceptions
• Deploy intrusion detection systems (IDS) with signatures for known JNDI-related attack patterns
• Monitor for repeated connection attempts or request patterns that may indicate exploitation attempts

Monitoring Recommendations

• Enable verbose logging for Java applications utilizing JNDI components to capture detailed error information
• Establish baseline metrics for application availability and alert on deviations indicating potential DoS conditions
• Implement application performance monitoring (APM) to detect partial service degradation in real-time
• Review security event logs for patterns of failed JNDI operations correlated with external network access

How to Mitigate CVE-2021-2432

Immediate Actions Required

• Inventory all systems running Oracle Java SE 7u301 to identify vulnerable deployments
• Prioritize upgrading Java SE to a supported version with security patches applied
• Restrict network access to Java applications using JNDI components where possible
• For McAfee ePolicy Orchestrator users, upgrade to version 5.10.0 Update 11 or later

Patch Information

Oracle has addressed this vulnerability in their Critical Patch Update. Organizations should apply the appropriate patches:

• Oracle Java SE: Upgrade from Java SE 7u301 to a patched version as outlined in the Oracle CPU July 2021 Alert. Additional guidance is available in the Oracle CPU October 2021 Alert.

• McAfee ePolicy Orchestrator: Apply the fix detailed in the McAfee Security Bulletin SB10366. Upgrade to ePolicy Orchestrator 5.10.0 Update 11 or later.

• NetApp Products: Refer to the NetApp Security Advisory NTAP-20210723-0002 for product-specific guidance.

• Gentoo Linux: Apply updates per Gentoo GLSA 202209-05.

Workarounds

• Disable Java Web Start applications and Java applets in browsers where not required for business operations
• Implement network segmentation to limit exposure of vulnerable Java applications to untrusted networks
• Apply firewall rules to restrict access to services utilizing JNDI components to trusted IP addresses only
• Consider deploying a Web Application Firewall (WAF) to filter malicious requests targeting Java applications

# Example: Restrict Java application network access using iptables
# Allow only specific trusted IP ranges to access Java application port
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP