CVE-2021-1993: Oracle Database Java VM Privilege Escalation

CVE-2021-1993 Overview

CVE-2021-1993 is a vulnerability in the Java VM component of Oracle Database Server. This flaw affects supported versions including 12.1.0.2, 12.2.0.1, 18c, and 19c. The vulnerability is difficult to exploit but allows a low-privileged attacker with Create Session privilege and network access via Oracle Net to compromise the Java VM component. Exploitation requires human interaction from a person other than the attacker and can result in unauthorized creation, deletion, or modification of critical data within the Java VM accessible data scope.

Critical Impact

Successful exploitation enables unauthorized modification or deletion of critical data accessible through the Java VM component, posing significant integrity risks to Oracle Database deployments.

Affected Products

• Oracle Database Server versions 12.1.0.2, 12.2.0.1, 18c, and 19c
• Oracle Enterprise Manager Ops Center 12.4.0.0
• Oracle Hyperion Infrastructure Technology 11.1.2.4
• Oracle ZFS Storage Appliance 8.8

Discovery Timeline

• 2021-01-20 - CVE-2021-1993 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-1993

Vulnerability Analysis

This vulnerability affects the Java VM component within Oracle Database Server, a critical subsystem that enables Java code execution within the database environment. The flaw allows attackers with low privileges (specifically, those holding the Create Session privilege) to compromise the integrity of data accessible through the Java VM.

The attack requires network access via Oracle Net, Oracle's proprietary networking protocol, and necessitates human interaction from a victim other than the attacker. While the vulnerability does not impact confidentiality or availability, it poses a significant integrity risk, potentially allowing unauthorized creation, deletion, or modification of critical data within the Java VM's accessible scope.

Root Cause

The vulnerability stems from an improper access control issue within the Java VM component of Oracle Database Server. The flaw allows users with Create Session privileges to perform unauthorized data modifications through the Java VM interface when specific conditions are met, including victim interaction. The exact technical mechanism has not been publicly disclosed by Oracle, consistent with their limited disclosure policy for database vulnerabilities.

Attack Vector

The attack vector is network-based and requires the attacker to have Oracle Net connectivity to the target database. The exploitation path involves:

1. The attacker must possess a valid low-privileged database account with Create Session privilege
2. Network access via Oracle Net protocol to the target database instance
3. Human interaction from a person other than the attacker (such as a database administrator or privileged user)
4. Successful exploitation results in integrity compromise of Java VM accessible data

The vulnerability exploitation is considered difficult due to the combination of required privileges, network positioning, and the mandatory human interaction component.

Detection Methods for CVE-2021-1993

Indicators of Compromise

• Unusual database session activity from accounts with Create Session privilege accessing Java VM components
• Unexpected data modifications in tables or objects accessible through the Java VM interface
• Anomalous Oracle Net traffic patterns targeting Java VM-enabled database instances

Detection Strategies

• Monitor Oracle Database audit logs for suspicious Java VM component access from low-privileged accounts
• Implement database activity monitoring to track Create Session privilege usage and correlate with Java VM operations
• Review Oracle Net connection logs for unusual access patterns to affected database versions

Monitoring Recommendations

• Enable Oracle Database fine-grained auditing on Java VM component operations
• Configure alerts for data modification attempts through Java VM from accounts that typically only read data
• Establish baselines for normal Java VM usage patterns to detect anomalous activity

How to Mitigate CVE-2021-1993

Immediate Actions Required

• Apply the Oracle Critical Patch Update (CPU) from January 2021 to all affected Oracle Database Server instances
• Review and restrict Create Session privileges to only essential users
• Audit user accounts with access to Java VM functionality within the database

Patch Information

Oracle has addressed this vulnerability in the Oracle Critical Patch Update January 2021. Organizations running Oracle Database Server versions 12.1.0.2, 12.2.0.1, 18c, or 19c should apply the appropriate patches as documented in the advisory. The patch also addresses related vulnerabilities in Oracle Enterprise Manager Ops Center, Oracle Hyperion Infrastructure Technology, and Oracle ZFS Storage Appliance.

Workarounds

• Restrict network access to Oracle Database instances via Oracle Net using firewall rules and network segmentation
• Revoke Create Session privilege from accounts that do not require database connectivity
• Disable Java VM component in Oracle Database if not required for business operations using ALTER SYSTEM commands
• Implement strict access controls and principle of least privilege for database accounts

# Configuration example - Disable Java VM if not required
# Connect as SYSDBA and execute:
# ALTER SYSTEM SET java_jit_enabled = FALSE SCOPE = BOTH;
# Note: Full Java VM removal may require database reinstallation
# Consult Oracle documentation before making changes