CVE-2021-2035: Oracle RDBMS Scheduler Privilege Escalation

CVE-2021-2035 Overview

CVE-2021-2035 is a privilege escalation vulnerability in the RDBMS Scheduler component of Oracle Database Server. This vulnerability allows a low-privileged attacker with the "Export Full Database" privilege to completely compromise the RDBMS Scheduler component through network access via Oracle Net protocol. The vulnerability is classified as easily exploitable and can result in a complete takeover of the affected component, impacting confidentiality, integrity, and availability.

Critical Impact

Successful exploitation allows attackers with limited database privileges to gain complete control over the RDBMS Scheduler component, potentially enabling unauthorized data access, modification, and service disruption across the Oracle Database Server environment.

Affected Products

• Oracle RDBMS Scheduler 12.1.0.2
• Oracle RDBMS Scheduler 12.2.0.1
• Oracle RDBMS Scheduler 18c
• Oracle RDBMS Scheduler 19c

Discovery Timeline

• 2021-01-20 - CVE-2021-2035 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-2035

Vulnerability Analysis

This vulnerability exists within the RDBMS Scheduler component, which is responsible for automating and scheduling database tasks within Oracle Database Server. The flaw enables privilege escalation where an attacker with the relatively low-level "Export Full Database" privilege can leverage network access to escalate their privileges and take complete control of the Scheduler component.

The attack requires network access via Oracle Net, Oracle's proprietary networking protocol used for database communication. Once exploited, the attacker gains the ability to impact all three pillars of the CIA triad—confidentiality, integrity, and availability—within the context of the RDBMS Scheduler.

Root Cause

The root cause of this vulnerability stems from improper access control validation within the RDBMS Scheduler component. The component fails to properly verify that users with the "Export Full Database" privilege should not have elevated access to Scheduler operations. This improper authorization check allows low-privileged users to perform actions that should be restricted to database administrators.

Attack Vector

The attack vector is network-based, utilizing the Oracle Net protocol for communication. An attacker must first obtain valid database credentials with the "Export Full Database" privilege. This privilege is commonly assigned to backup operators and database maintenance accounts, making it a realistic attack scenario in enterprise environments.

The attack flow involves:

1. Authenticating to the Oracle Database Server with credentials possessing the "Export Full Database" privilege
2. Connecting via Oracle Net to the RDBMS Scheduler component
3. Exploiting the improper authorization checks to escalate privileges within the Scheduler context
4. Achieving complete control over Scheduler operations, including the ability to execute arbitrary scheduled tasks

The vulnerability does not require user interaction and has low attack complexity, making it attractive to threat actors targeting Oracle database environments.

Detection Methods for CVE-2021-2035

Indicators of Compromise

• Unusual database connection attempts from accounts with "Export Full Database" privilege targeting Scheduler-related objects
• Unexpected scheduled job creation, modification, or execution by non-administrative accounts
• Anomalous Oracle Net traffic patterns to the RDBMS Scheduler component
• Audit log entries showing privilege escalation attempts within the Scheduler subsystem

Detection Strategies

• Enable Oracle Database Unified Auditing to capture all Scheduler-related operations and privilege usage
• Monitor for unusual DBMS_SCHEDULER package calls from accounts that typically only perform export operations
• Implement network traffic analysis on Oracle Net protocol to detect suspicious Scheduler interactions
• Review Oracle alert logs for authentication anomalies and Scheduler component errors

Monitoring Recommendations

• Configure fine-grained auditing on the SYS.DBMS_SCHEDULER package and related Scheduler objects
• Deploy database activity monitoring (DAM) solutions to track all Scheduler API calls
• Establish baseline behavior for accounts with "Export Full Database" privilege and alert on deviations
• Integrate Oracle Database audit logs with SIEM platforms for correlation with other network events

How to Mitigate CVE-2021-2035

Immediate Actions Required

• Apply the Oracle Critical Patch Update (CPU) from January 2021 to all affected Oracle Database Server installations
• Review and restrict the "Export Full Database" privilege to only essential accounts
• Implement network segmentation to limit Oracle Net access to the database server from trusted hosts only
• Audit all accounts with the "Export Full Database" privilege and verify legitimate business need

Patch Information

Oracle has addressed this vulnerability in the January 2021 Critical Patch Update (CPU). Administrators should download and apply the appropriate patch from the Oracle Security Alert - January 2021. The patch corrects the authorization checks within the RDBMS Scheduler component to properly validate user privileges before allowing sensitive operations.

Affected versions requiring patching:

• 12.1.0.2
• 12.2.0.1
• 18c
• 19c

Workarounds

• Revoke the "Export Full Database" privilege from accounts that do not have an absolute business requirement for this access level
• Implement database firewall rules to restrict Oracle Net connections to the Scheduler component from non-administrative clients
• Use Oracle Database Vault to create additional access controls around Scheduler operations
• Enable Oracle Label Security to add mandatory access controls that supplement standard privilege checks

# Example: Auditing Scheduler operations for detection
# Enable unified auditing for DBMS_SCHEDULER package
ALTER SYSTEM SET AUDIT_TRAIL=DB,EXTENDED SCOPE=SPFILE;

# Create audit policy for Scheduler monitoring
CREATE AUDIT POLICY scheduler_audit_policy
ACTIONS ALL ON SYS.DBMS_SCHEDULER;

# Enable the audit policy for all users
AUDIT POLICY scheduler_audit_policy;