CVE-2001-0951 in Windows
Summary
by MITRE
Windows 2000 allows remote attackers to cause a denial of service (CPU consumption) by flooding Internet Key Exchange (IKE) UDP port 500 with packets that contain a large number of dot characters.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/02/2025
The vulnerability described in CVE-2001-0951 represents a significant denial of service weakness in Microsoft Windows 2000 operating systems that specifically targets the Internet Key Exchange protocol implementation. This flaw manifests when the system receives malformed IKE packets containing an excessive number of dot characters on UDP port 500, which is the standard port used for IKE communications in IPsec VPN implementations. The vulnerability operates at the network protocol level and demonstrates how improper input validation can lead to system resource exhaustion and operational disruption.
The technical mechanism behind this vulnerability involves the IKE daemon's insufficient validation of incoming packet contents, particularly when processing authentication and key exchange messages. When Windows 2000 receives IKE packets with excessive dot character sequences, the system's processing logic becomes inefficient and consumes disproportionate CPU resources during the parsing and validation phases. This behavior aligns with CWE-129, which describes improper validation of array indices, and CWE-131, which addresses insufficient control of the length of a control message. The vulnerability essentially creates a condition where the system's CPU utilization spikes to 100% as it attempts to process these malformed packets, effectively rendering the machine unable to handle legitimate network traffic or perform normal system operations.
From an operational perspective, this vulnerability presents a serious risk to network infrastructure security and availability. Attackers can exploit this weakness by sending a relatively small number of specially crafted packets to the target system's UDP port 500, causing sustained high CPU consumption that leads to complete system unresponsiveness. This type of attack falls under the ATT&CK technique T1498, specifically targeting network denial of service, and represents a classic example of a resource exhaustion attack that can be executed with minimal technical expertise. The impact extends beyond simple service disruption as it can affect the entire network infrastructure, particularly in environments where Windows 2000 systems serve as VPN gateways or network security appliances.
The mitigation strategies for this vulnerability include implementing network-level filtering to restrict access to UDP port 500 from unauthorized sources, applying Microsoft security patches that address the IKE processing flaws, and configuring rate limiting on incoming IKE traffic to prevent excessive packet processing. Organizations should also consider deploying intrusion detection systems that can identify and alert on abnormal IKE packet patterns, as well as implementing network segmentation to isolate vulnerable systems from critical network components. Additionally, system administrators should monitor CPU utilization patterns and implement automated response mechanisms that can detect and mitigate such attacks before they cause significant service disruption. The vulnerability underscores the importance of proper input validation and resource management in network protocol implementations, and serves as a reminder of the critical need for regular security updates and comprehensive network monitoring practices.