CVE-2024-21208 Overview
CVE-2024-21208 is a denial of service vulnerability affecting the Networking component of Oracle Java SE, Oracle GraalVM for JDK, and Oracle GraalVM Enterprise Edition. This vulnerability allows an unauthenticated attacker with network access via multiple protocols to cause a partial denial of service condition. The vulnerability is classified as CWE-203 (Observable Discrepancy), indicating potential information exposure through timing or behavioral differences in the networking stack.
Critical Impact
Unauthenticated attackers can remotely trigger partial denial of service conditions in Java applications, particularly impacting client-side deployments running sandboxed Java Web Start applications or Java applets that process untrusted code from the internet.
Affected Products
- Oracle Java SE: 8u421, 8u421-perf, 11.0.24, 17.0.12, 21.0.4, 23
- Oracle GraalVM for JDK: 17.0.12, 21.0.4, 23
- Oracle GraalVM Enterprise Edition: 20.3.15, 21.3.11
Discovery Timeline
- October 15, 2024 - CVE-2024-21208 published to NVD
- November 3, 2025 - Last updated in NVD database
Technical Details for CVE-2024-21208
Vulnerability Analysis
This vulnerability resides in the Networking component of Oracle's Java platform implementations. The flaw allows remote attackers to trigger a partial denial of service without requiring any privileges or user interaction. The vulnerability specifically impacts Java deployments in client environments where sandboxed Java Web Start applications or Java applets load and execute untrusted code from external sources such as the internet.
The attack complexity is high, meaning successful exploitation requires specific conditions or circumstances to be present. Importantly, this vulnerability does not affect server-side Java deployments that exclusively load and run trusted code installed by administrators. The scope is unchanged, meaning the vulnerable component and impacted component are the same, and the impact is limited to availability with no effect on confidentiality or integrity.
Root Cause
The root cause is tied to CWE-203 (Observable Discrepancy), which indicates the networking component may expose information through observable differences in behavior or timing. This type of vulnerability occurs when a system reveals sensitive information through side channels such as response times, error messages, or other behavioral characteristics that differ based on internal state or data processing. In the context of Java's networking stack, this could allow attackers to infer information about network operations or manipulate connections to cause service disruption.
Attack Vector
The attack is conducted over the network using multiple protocols supported by the Java networking stack. An unauthenticated attacker can remotely target vulnerable Java client applications that process untrusted content.
The exploitation scenario typically involves:
- A victim running a sandboxed Java application (Web Start or applet) that relies on the Java sandbox for security
- The application loading and executing untrusted code from the internet
- The attacker crafting network traffic or content that exploits the observable discrepancy in the networking component
- Successful exploitation results in partial denial of service, degrading the availability of the Java application
Server-side deployments running only trusted, administrator-installed code are not affected by this vulnerability.
Detection Methods for CVE-2024-21208
Indicators of Compromise
- Unusual network connection patterns or repeated connection failures in Java applications
- Unexpected resource consumption or performance degradation in Java client applications processing external content
- Log entries indicating networking errors or exceptions in sandboxed Java environments
- Anomalous behavior in Java Web Start applications or applets when loading remote content
Detection Strategies
- Monitor Java application logs for networking component errors and exceptions related to connection handling
- Implement network traffic analysis to detect anomalous patterns targeting Java client applications
- Deploy endpoint detection and response (EDR) solutions to monitor for unusual Java process behavior
- Track Java runtime performance metrics for unexpected availability degradation
Monitoring Recommendations
- Enable verbose logging for Java networking operations in client deployments handling untrusted content
- Implement application performance monitoring (APM) to detect partial denial of service conditions
- Configure alerting for repeated network-related exceptions in Java applications
- Monitor system resources (CPU, memory, network connections) for Java processes executing sandboxed code
How to Mitigate CVE-2024-21208
Immediate Actions Required
- Identify all systems running affected versions of Oracle Java SE, Oracle GraalVM for JDK, and Oracle GraalVM Enterprise Edition
- Prioritize patching for client-side deployments running sandboxed Java applications that process untrusted internet content
- Review and restrict the use of Java Web Start applications and Java applets where possible
- Implement network segmentation to limit exposure of vulnerable Java clients
Patch Information
Oracle has released security patches addressing this vulnerability as part of the October 2024 Critical Patch Update. Administrators should upgrade to the latest supported versions of the affected products. For detailed patch information and download links, refer to the Oracle Security Alert October 2024.
Additional vendor advisories are available from:
Workarounds
- Disable or restrict Java Web Start and applet functionality if not required for business operations
- Implement strict content filtering to prevent loading of untrusted Java content from the internet
- Deploy web application firewalls (WAF) or network security appliances to filter potentially malicious traffic targeting Java applications
- Consider migrating away from legacy Java applet and Web Start technologies to modern alternatives
# Verify installed Java version to assess vulnerability
java -version
# Check for vulnerable JDK installations
find /usr -name "java" -exec {} -version 2>&1 \; | grep -E "(1.8.0_421|11.0.24|17.0.12|21.0.4|23)"
# Disable Java Web Start if not needed (example for Linux)
update-alternatives --remove javaws /usr/bin/javaws
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
