CVE-2020-2654: Oracle JDK Libraries DoS Vulnerability

CVE-2020-2654 Overview

CVE-2020-2654 is a denial of service vulnerability affecting the Libraries component of Oracle Java SE. This vulnerability exists in multiple supported Java versions and can be exploited by an unauthenticated attacker with network access via multiple protocols. While the vulnerability is considered difficult to exploit, successful attacks can result in an unauthorized ability to cause a partial denial of service (partial DoS) of Java SE.

Notably, this vulnerability cannot be exploited through Untrusted Java Web Start applications or Untrusted Java applets. Instead, exploitation requires supplying malicious data to APIs in the affected Libraries component, such as through a web service interface.

Critical Impact

Successful exploitation allows remote unauthenticated attackers to cause partial denial of service conditions in Java SE applications processing specially crafted data through the Libraries component.

Affected Products

• Oracle JDK 7u241, 8u231, 11.0.5, and 13.0.1
• Oracle JRE 7u241, 8u231, 11.0.5, and 13.0.1
• Oracle OpenJDK 7, 8, 11, and 13 (various updates)
• Red Hat Enterprise Linux 6.0, 7.0, and 8.0
• Debian Linux 8.0, 9.0, and 10.0
• Canonical Ubuntu Linux 16.04 LTS, 18.04 LTS, and 19.10
• NetApp Active IQ Unified Manager, E-Series products, OnCommand Insight
• McAfee ePolicy Orchestrator 5.9.x and 5.10.x
• openSUSE Leap 15.1

Discovery Timeline

• 2020-01-15 - CVE-2020-2654 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-2654

Vulnerability Analysis

This vulnerability resides within the Libraries component of Oracle Java SE, which encompasses core Java class libraries used extensively throughout Java applications. The flaw allows an unauthenticated attacker with network access to supply specially crafted data to APIs within the Libraries component, potentially causing resource exhaustion or processing anomalies that result in partial service disruption.

The attack surface is limited to scenarios where Java applications accept and process external data through vulnerable API endpoints. The high attack complexity required for exploitation means that successful attacks depend on specific conditions being met, such as particular data patterns or timing requirements.

The impact is confined to availability concerns, with no confidentiality or integrity violations. Applications that process untrusted input through affected library functions are at risk of experiencing service degradation or intermittent failures when targeted.

Root Cause

The vulnerability stems from insufficient input validation or resource handling within specific functions in the Java SE Libraries component. When processing certain types of malformed or specially crafted input data, the affected code paths may consume excessive resources or enter inefficient processing states. The exact technical root cause relates to how the Libraries component handles edge cases in data processing, leading to potential resource exhaustion under specific conditions.

Attack Vector

The attack vector for CVE-2020-2654 requires network access and involves supplying malicious data to vulnerable APIs within the Java SE Libraries component. Key characteristics of the attack include:

• Network-based exploitation: Attackers must have network connectivity to the target application
• No authentication required: The vulnerability can be exploited without credentials
• No user interaction needed: Exploitation does not require user participation
• API-based attack surface: Malicious data is supplied through programmatic interfaces, not through browser-based applets or Web Start applications
• Service-oriented targets: Web services and applications accepting external data are primary targets

The attacker crafts specific input data designed to trigger the vulnerable code path in the Libraries component. When a Java application processes this data through affected APIs, it may experience degraded performance or partial service interruption.

Detection Methods for CVE-2020-2654

Indicators of Compromise

• Unusual patterns of malformed requests targeting Java-based web services or APIs
• Increased resource consumption (CPU, memory) in Java processes without corresponding legitimate workload increases
• Application log entries indicating unexpected exceptions or errors in Libraries component classes
• Intermittent service degradation affecting Java applications processing external data

Detection Strategies

• Monitor Java application logs for unusual exception patterns related to input processing
• Implement network traffic analysis to detect anomalous request patterns targeting Java services
• Deploy application performance monitoring to identify sudden spikes in resource utilization
• Configure alerting on Java Virtual Machine (JVM) metrics indicating abnormal garbage collection or memory pressure

Monitoring Recommendations

• Enable verbose logging for Java applications processing external data to capture detailed error information
• Implement rate limiting on API endpoints that accept external input to mitigate DoS attempts
• Configure JVM monitoring tools to track heap usage, thread counts, and CPU utilization
• Establish baseline performance metrics to quickly identify deviations indicative of exploitation attempts

How to Mitigate CVE-2020-2654

Immediate Actions Required

• Update all Oracle JDK and JRE installations to patched versions released after January 2020
• Review and update OpenJDK installations to fixed versions
• Apply operating system vendor patches for bundled Java packages (Red Hat, Debian, Ubuntu, openSUSE)
• Update third-party applications that bundle Java runtimes (NetApp, McAfee products)
• Conduct an inventory of all Java installations to ensure comprehensive patching

Patch Information

Oracle addressed this vulnerability in their January 2020 Critical Patch Update (CPU). The Oracle Security Alert CPUJAN2020 provides official patch information and download links for affected products.

Multiple Linux distributions have released corresponding security updates:

• Red Hat: Multiple RHSA advisories including RHSA-2020:0122, RHSA-2020:0128, and others
• Debian: DSA-4605 and DSA-4621
• Ubuntu: USN-4257-1
• Gentoo: GLSA-202101-19
• NetApp: NTAP-20200122-0003
• McAfee: SB10315

Workarounds

• Implement input validation and sanitization at the application layer before data reaches Java APIs
• Deploy Web Application Firewalls (WAF) to filter potentially malicious requests
• Restrict network access to Java services to trusted sources only
• Consider implementing circuit breakers in applications to limit the impact of resource exhaustion

# Verify Java version after patching
java -version

# For Red Hat/CentOS systems, update Java packages
sudo yum update java-1.8.0-openjdk java-11-openjdk

# For Debian/Ubuntu systems, update Java packages
sudo apt-get update && sudo apt-get upgrade openjdk-8-jdk openjdk-11-jdk