CVE-2021-2341: Oracle OpenJDK Information Disclosure Flaw

CVE-2021-2341 Overview

CVE-2021-2341 is an information disclosure vulnerability affecting the Networking component of Oracle Java SE and Oracle GraalVM Enterprise Edition. This vulnerability allows an unauthenticated attacker with network access via multiple protocols to potentially gain unauthorized read access to a subset of accessible data within affected Java deployments.

The vulnerability specifically impacts Java deployments running sandboxed Java Web Start applications or sandboxed Java applets that load and execute untrusted code from external sources such as the internet. These deployments rely on the Java sandbox for security isolation, making them susceptible when the Networking component fails to properly restrict data access. Importantly, server-side Java deployments that only load and run trusted, administrator-installed code are not affected by this vulnerability.

Critical Impact

Successful exploitation enables unauthorized read access to sensitive data in sandboxed Java client applications, potentially exposing confidential information to remote attackers.

Affected Products

• Oracle Java SE: 7u301, 8u291, 11.0.11, 16.0.1
• Oracle GraalVM Enterprise Edition: 20.3.2 and 21.1.0
• Oracle OpenJDK: Multiple versions across 7, 8, 11, 13, 15, and 16 branches
• Debian Linux: 9.0 and 10.0
• Fedora: 33 and 34

Discovery Timeline

• July 21, 2021 - CVE-2021-2341 published to NVD
• May 27, 2025 - Last updated in NVD database

Technical Details for CVE-2021-2341

Vulnerability Analysis

This vulnerability exists within the Networking component of Oracle Java SE and Oracle GraalVM Enterprise Edition. The flaw allows an unauthenticated attacker to potentially read a subset of data that should be protected by the Java sandbox security model.

The exploitation scenario requires specific conditions to be met: the attacker must have network access, the attack is difficult to execute (high attack complexity), and successful exploitation requires human interaction from a person other than the attacker. The impact is limited to confidentiality—there is no effect on data integrity or system availability.

The vulnerability primarily affects client-side Java deployments where untrusted code is executed within a sandboxed environment. Java Web Start applications and Java applets that load remote, untrusted code are the primary attack surface. Server deployments running only trusted, locally-installed code are not vulnerable to this issue.

Root Cause

The root cause stems from insufficient access controls within the Java Networking component when handling network operations in sandboxed environments. The specific technical details have not been publicly disclosed by Oracle, as indicated by the CWE classification of "NVD-CWE-noinfo." However, the vulnerability allows the sandbox security boundary to be partially bypassed, enabling unauthorized read access to data that should otherwise be restricted.

Attack Vector

Exploitation of CVE-2021-2341 requires an attacker to craft malicious content that can be loaded by a sandboxed Java application. The attack vector is network-based, meaning the attacker delivers the exploit payload over a network connection.

The attack flow typically involves:

1. An attacker creates a malicious Java Web Start application or Java applet
2. A victim is socially engineered to access a website or resource containing the malicious content
3. The victim's browser or Java Web Start launches the sandboxed Java application
4. The malicious code exploits the vulnerability in the Networking component
5. The attacker gains unauthorized read access to a subset of data accessible by the Java process

Due to the high attack complexity and requirement for user interaction, the vulnerability is considered difficult to exploit reliably. The attacker must overcome both technical challenges in crafting a reliable exploit and the social engineering aspect of convincing a user to interact with the malicious content.

Detection Methods for CVE-2021-2341

Indicators of Compromise

• Unexpected network connections initiated by Java Web Start applications or Java applets
• Unusual data exfiltration patterns from sandboxed Java processes
• Java processes accessing files or network resources outside their expected scope
• Anomalous behavior in browser plugins related to Java applet execution

Detection Strategies

• Monitor Java process network activity for connections to unknown or suspicious external hosts
• Implement egress filtering to detect and alert on unexpected outbound connections from Java runtime environments
• Use endpoint detection solutions to identify Java processes exhibiting anomalous file or network access patterns
• Review application logs for Java Web Start or applet executions from untrusted sources

Monitoring Recommendations

• Enable verbose logging for Java Web Start and applet executions in client environments
• Deploy network monitoring to track Java process communications across organizational boundaries
• Implement SentinelOne endpoint protection to detect and respond to suspicious Java runtime behaviors
• Configure alerts for Java applications attempting to access sensitive data stores or network resources

How to Mitigate CVE-2021-2341

Immediate Actions Required

• Update Oracle Java SE to versions 7u311, 8u301, 11.0.12, or 16.0.2 or later
• Upgrade Oracle GraalVM Enterprise Edition to version 20.3.3 or 21.2.0 or later
• Apply available security patches from Debian, Fedora, and other Linux distributions
• Disable Java Web Start and Java applets if not required for business operations
• Review and restrict which applications are permitted to execute untrusted Java code

Patch Information

Oracle addressed this vulnerability as part of the Oracle CPU July 2021 Security Alert. Additional updates were provided in the Oracle CPU October 2021 Security Alert.

Linux distributions have also released patches:

• Debian: Debian Security Advisory DSA-4946 and Debian LTS Announcement
• Fedora: Package updates available via Fedora Package Announcements
• Gentoo: Gentoo GLSA 202209-05
• NetApp: NetApp Security Advisory NTAP-20210723-0002

Workarounds

• Disable Java Web Start and Java browser plugins in enterprise environments where not required
• Configure network firewalls to restrict outbound connections from Java processes to only approved destinations
• Implement application whitelisting to prevent execution of untrusted Java code
• Use browser security policies to block Java applet execution from untrusted domains

# Disable Java Web Start associations (Windows example)
# Remove file associations for .jnlp files
assoc .jnlp=

# On Linux, restrict Java plugin in browsers
# Remove Java browser plugin symlinks
sudo rm -f /usr/lib/mozilla/plugins/libnpjp2.so
sudo rm -f /usr/lib64/mozilla/plugins/libnpjp2.so