CVE-2023-21937 Overview
CVE-2023-21937 is a networking component vulnerability in Oracle Java SE and Oracle GraalVM Enterprise Edition. The flaw allows an unauthenticated attacker with network access via multiple protocols to compromise affected systems. While the vulnerability is difficult to exploit, successful attacks can result in unauthorized update, insert, or delete access to some accessible data within Java SE and GraalVM Enterprise Edition environments.
This vulnerability is particularly concerning for Java deployments that run sandboxed Java Web Start applications or sandboxed Java applets that load and run untrusted code from the internet and rely on the Java sandbox for security. The vulnerability can also be exploited through APIs in the Networking component, such as through web services that supply data to the APIs.
Critical Impact
Attackers can perform unauthorized data modifications in Java SE and GraalVM Enterprise Edition environments through network-based exploitation of the Networking component.
Affected Products
- Oracle Java SE: 8u361, 8u361-perf, 11.0.18, 17.0.6, 20
- Oracle GraalVM Enterprise Edition: 20.3.9, 21.3.5, 22.3.1
- Oracle JDK and JRE: 1.8.0 update 361, 11.0.18, 17.0.6, 20
- Oracle OpenJDK: Multiple versions including 8 through update 362, and version 20
- NetApp 7-Mode Transition Tool
- NetApp Brocade SAN Navigator
- NetApp Cloud Insights Acquisition Unit
- NetApp Cloud Insights Storage Workload Security Agent
- NetApp OnCommand Insight
- Debian Linux: 10.0, 11.0, 12.0
Discovery Timeline
- April 18, 2023 - CVE-2023-21937 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2023-21937
Vulnerability Analysis
The vulnerability resides in the Networking component of Oracle Java SE and Oracle GraalVM Enterprise Edition. The flaw stems from improper handling of network operations, which can be exploited by an unauthenticated attacker with network access. The attack complexity is considered high, meaning successful exploitation requires specific conditions to be met.
The vulnerability specifically impacts Java deployments in client environments where sandboxed applications execute untrusted code. This includes Java Web Start applications and Java applets that load code from external sources and depend on the Java sandbox security model. Additionally, the vulnerability can be triggered through APIs exposed by the Networking component, making web services that interface with these APIs potential attack vectors.
Root Cause
The root cause of CVE-2023-21937 is related to improper handling within the Networking component of Java SE and GraalVM Enterprise Edition. While Oracle has not disclosed the specific technical details of the underlying flaw, the vulnerability classification indicates an integrity-related issue that allows unauthorized data modification. The Networking component handles various network protocols and connections, and the flaw appears to affect how certain network operations process or validate data.
Attack Vector
The attack vector for this vulnerability is network-based, requiring the attacker to have network access to the target system. The exploitation can occur through multiple protocols, indicating the vulnerability is not limited to a single network protocol implementation.
The attack scenario typically involves:
- An attacker identifying a Java application that uses the vulnerable Networking component
- Sending specially crafted network requests that trigger the vulnerability
- Exploiting the flaw to perform unauthorized data modifications
For client-side exploitation, the attacker would need to convince a user to load malicious Java code (such as through a Java applet or Web Start application) that then exploits the vulnerability. For server-side exploitation, the attacker would target web services or APIs that utilize the vulnerable Networking component.
Due to the high attack complexity, successful exploitation requires precise timing or specific environmental conditions, reducing the likelihood of widespread automated exploitation.
Detection Methods for CVE-2023-21937
Indicators of Compromise
- Unusual network traffic patterns from Java applications to unexpected destinations
- Unexpected data modifications in applications relying on Java SE or GraalVM networking functions
- Anomalous API calls to Java Networking component functions from untrusted sources
- Java applet or Web Start application activity from suspicious sources
Detection Strategies
- Monitor Java application logs for unusual networking activity or errors in the Networking component
- Implement network intrusion detection rules to identify suspicious traffic patterns targeting Java applications
- Deploy application security monitoring to detect unauthorized data modification attempts
- Track execution of sandboxed Java applications and their network communications
Monitoring Recommendations
- Enable verbose logging for Java applications to capture Networking component activities
- Implement file integrity monitoring on systems running affected Java versions to detect unauthorized changes
- Monitor for new or unusual Java Web Start applications and applets being executed in the environment
- Configure SIEM rules to correlate Java application network activity with potential exploitation attempts
How to Mitigate CVE-2023-21937
Immediate Actions Required
- Update Oracle Java SE to version 8u371 or later, 11.0.19 or later, 17.0.7 or later, or 21 or later
- Update Oracle GraalVM Enterprise Edition to the latest patched version
- Review and restrict execution of untrusted Java applets and Web Start applications
- Audit web services that utilize Java Networking APIs for potential exposure
Patch Information
Oracle has released patches for this vulnerability as part of the April 2023 Critical Patch Update (CPU). Organizations should apply the appropriate updates based on their Java SE or GraalVM Enterprise Edition version:
- For Oracle Java SE, refer to the Oracle Security Alert CPUAPR2023
- For Debian Linux systems, apply updates from Debian Security Advisory DSA-5430 or DSA-5478
- For NetApp products, consult the NetApp Security Advisory NTAP-20230427-0008
- For OpenJDK, update to the latest available patched release
Workarounds
- Disable Java Web Start and Java applets in browser settings if not required for business operations
- Implement network segmentation to isolate Java applications from untrusted network segments
- Use application whitelisting to prevent execution of untrusted Java code
- Configure Java Security Manager policies to restrict Networking component capabilities for sandboxed applications
# Configuration example
# Restrict Java Web Start and applet execution via deployment.properties
echo "deployment.webjava.enabled=false" >> /etc/.java/deployment/deployment.properties
echo "deployment.security.level=VERY_HIGH" >> /etc/.java/deployment/deployment.properties
# Verify Java version after patching
java -version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
