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CVE Vulnerability Database
Vulnerability Database/CVE-2024-21126

CVE-2024-21126: Oracle Database Server DOS Vulnerability

CVE-2024-21126 is a denial of service vulnerability in Oracle Database Portable Clusterware that allows unauthenticated attackers to cause partial DOS via DNS. This article covers technical details, affected versions, and mitigation.

Updated: January 22, 2026

CVE-2024-21126 Overview

CVE-2024-21126 is a denial of service vulnerability in the Oracle Database Portable Clusterware component of Oracle Database Server. This vulnerability allows an unauthenticated attacker with network access via DNS to cause a partial denial of service against the affected component. Due to the scope change characteristic, successful exploitation can significantly impact additional products beyond the vulnerable component itself.

Critical Impact

Unauthenticated attackers can remotely trigger partial denial of service conditions in Oracle Database Portable Clusterware via DNS, with potential cascading effects on dependent systems.

Affected Products

  • Oracle Database Server versions 19.3-19.23
  • Oracle Database Server versions 21.3-21.14
  • Oracle Database Portable Clusterware component

Discovery Timeline

  • 2024-07-16 - CVE-2024-21126 published to NVD
  • 2025-06-18 - Last updated in NVD database

Technical Details for CVE-2024-21126

Vulnerability Analysis

This vulnerability resides in the Oracle Database Portable Clusterware component, which is responsible for cluster management and high availability features within Oracle Database Server deployments. The flaw is classified as a resource exhaustion vulnerability (CWE-400), indicating that the component fails to properly manage system resources when processing certain DNS-related requests.

The vulnerability is easily exploitable, requiring no authentication or user interaction to trigger. An attacker can leverage network access via DNS protocols to compromise the availability of the Portable Clusterware component. The scope change characteristic indicates that while the vulnerable component is Oracle Database Portable Clusterware, successful attacks may significantly impact additional products that depend on or interact with the clusterware services.

Root Cause

The root cause is improper resource consumption management (CWE-400) within the Oracle Database Portable Clusterware component when handling DNS-based operations. The component fails to adequately limit or throttle resource allocation during DNS request processing, allowing an attacker to exhaust available resources and degrade service availability.

Attack Vector

The attack is conducted over the network via DNS protocols. An unauthenticated attacker can send specially crafted DNS requests to the vulnerable Portable Clusterware component. The attack requires no privileges or user interaction, making it straightforward to execute remotely. The vulnerability allows for partial denial of service, meaning that while the attack may not completely disable the service, it can significantly degrade performance and availability of the clusterware and potentially connected database systems.

The scope change in this vulnerability means that while the attack targets Oracle Database Portable Clusterware specifically, the impact can extend to other products and services that rely on the clusterware for cluster management and coordination functions.

Detection Methods for CVE-2024-21126

Indicators of Compromise

  • Unusual spikes in DNS traffic targeting Oracle Database Server infrastructure
  • Degraded performance or intermittent availability issues in Oracle Database Portable Clusterware services
  • Elevated resource consumption (CPU, memory, network) on database cluster nodes
  • Cluster synchronization failures or timeout errors in Oracle clusterware logs

Detection Strategies

  • Monitor DNS query patterns and volumes to database server infrastructure for anomalies
  • Implement network intrusion detection rules to identify suspicious DNS traffic patterns targeting Oracle services
  • Configure alerting on Oracle Database Portable Clusterware service availability and response times
  • Enable verbose logging on clusterware components to capture resource exhaustion events

Monitoring Recommendations

  • Deploy network monitoring to track DNS traffic flows to Oracle Database Server deployments
  • Establish baseline resource utilization metrics for Portable Clusterware components and alert on deviations
  • Monitor Oracle clusterware logs for error messages indicating resource constraints or DNS processing issues
  • Implement service availability monitoring for critical cluster coordination services

How to Mitigate CVE-2024-21126

Immediate Actions Required

  • Apply the security patches from Oracle's July 2024 Critical Patch Update immediately
  • Review network access controls to restrict DNS traffic sources that can reach Oracle Database Server infrastructure
  • Implement rate limiting on DNS queries to database cluster infrastructure
  • Enable enhanced monitoring on Oracle Database Portable Clusterware components

Patch Information

Oracle has released security patches addressing this vulnerability as part of the Oracle Critical Patch Update July 2024. Organizations running Oracle Database Server versions 19.3-19.23 or 21.3-21.14 should apply the relevant patches immediately.

For version 19.x deployments, upgrade to version 19.24 or later. For version 21.x deployments, upgrade to version 21.15 or later. Consult Oracle's security advisory for specific patch download links and installation instructions.

Workarounds

  • Restrict network access to Oracle Database Portable Clusterware services using firewall rules to limit DNS traffic sources
  • Implement DNS query rate limiting at the network perimeter to prevent resource exhaustion attacks
  • Consider deploying DNS security solutions that can filter malicious or excessive DNS requests
  • Isolate clusterware management interfaces from untrusted network segments where feasible
bash
# Example: Network firewall rule to restrict DNS access to trusted sources
# Adjust IP ranges according to your environment
iptables -A INPUT -p udp --dport 53 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 53 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p udp --dport 53 -j DROP
iptables -A INPUT -p tcp --dport 53 -j DROP

Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.

  • Vulnerability Details
  • TypeDOS
  • Vendor/TechOracle Database
  • SeverityMEDIUM
  • CVSS Score5.8
  • EPSS Probability0.19%
  • Known ExploitedNo
  • CVSS Vector
  • CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
  • Impact Assessment
  • ConfidentialityLow
  • IntegrityNone
  • AvailabilityLow
  • CWE References
  • CWE-400
  • Vendor Resources
  • Oracle Security Alert July 2024
  • Related CVEs
  • CVE-2026-21975: Oracle Database Java VM DoS Vulnerability
  • CVE-2024-21174: Oracle Database Server Java VM DoS Flaw
  • CVE-2022-21432: Oracle Database RDBMS DOS Vulnerability
  • CVE-2022-21393: Oracle Database Server Java VM DOS Flaw
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