CVE-2001-1244 in IRIX
Summary
by MITRE
Multiple TCP implementations could allow remote attackers to cause a denial of service (bandwidth and CPU exhaustion) by setting the maximum segment size (MSS) to a very small number and requesting large amounts of data, which generates more packets with less TCP-level data that amplify network traffic and consume more server CPU to process.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/02/2024
This vulnerability represents a significant flaw in TCP protocol implementations that affects network bandwidth and computational resources across multiple operating systems and network devices. The issue stems from how TCP stacks handle the maximum segment size parameter, which controls the largest amount of data that can be transmitted in a single TCP segment. When an attacker manipulates this parameter to extremely small values, typically below the standard minimum thresholds, the protocol behavior becomes inefficient and exploitable.
The technical exploitation occurs when an attacker establishes a TCP connection and deliberately sets the MSS to an abnormally small value, often as low as one byte or less. This manipulation forces the TCP stack to fragment large data transfers into numerous small packets, each carrying minimal payload information. The amplification effect becomes apparent when the attacker requests substantial amounts of data from the target system, causing the server to generate hundreds or thousands of packets for what should be a single large data transfer. This process consumes excessive network bandwidth as the small packets traverse the network infrastructure and simultaneously requires significant CPU cycles to process each individual packet header and handle the fragmented data streams.
The operational impact of this vulnerability extends beyond simple service disruption to encompass substantial resource exhaustion across network infrastructure. Network devices such as routers, firewalls, and load balancers experience increased processing overhead as they must handle the inflated packet count, leading to potential network congestion and performance degradation. Server systems face CPU utilization spikes that can approach 100% during sustained attacks, effectively preventing legitimate traffic processing and rendering services unavailable to genuine users. This vulnerability particularly affects systems that handle large file transfers, web content delivery, or any scenario where substantial data volumes are transmitted over TCP connections.
The vulnerability aligns with several cybersecurity frameworks and threat modeling approaches, including CWE-129 which addresses improper handling of buffer sizes and ATT&CK technique T1498 related to resource exhaustion attacks. This flaw demonstrates how fundamental protocol parameters can be manipulated to create cascading effects that compromise system availability. Network security professionals should consider implementing TCP stack hardening measures such as MSS value validation, rate limiting for connection establishment, and monitoring for unusual packet size patterns. Additionally, deploying intrusion detection systems that can identify and block anomalous TCP MSS values helps prevent exploitation of this vulnerability. Organizations should also ensure their TCP implementations properly validate and sanitize TCP options during connection establishment to prevent attackers from manipulating these parameters to create resource exhaustion conditions.