CVE-2007-4997 in Linux
Summary
by MITRE
Integer underflow in the ieee80211_rx function in net/ieee80211/ieee80211_rx.c in the Linux kernel 2.6.x before 2.6.23 allows remote attackers to cause a denial of service (crash) via a crafted SKB length value in a runt IEEE 802.11 frame when the IEEE80211_STYPE_QOS_DATA flag is set, aka an "off-by-two error."
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/31/2019
The vulnerability described in CVE-2007-4997 represents a critical integer underflow condition within the Linux kernel's wireless networking subsystem, specifically affecting versions prior to 2.6.23. This flaw exists in the ieee80211_rx function located in net/ieee80211/ieee80211_rx.c, which processes incoming IEEE 802.11 wireless frames. The issue manifests when a maliciously crafted IEEE 802.11 frame contains a runt frame with a specifically manipulated SKB (socket buffer) length value while simultaneously having the IEEE80211_STYPE_QOS_DATA flag set. This particular combination triggers a mathematical underflow condition in the kernel's frame processing logic, resulting in a system crash that constitutes a denial of service attack vector.
The technical nature of this vulnerability can be classified as a CWE-191 Integer Underflow (Wrap or Wraparound) according to the Common Weakness Enumeration standards. The flaw operates through an off-by-two error mechanism where integer arithmetic fails to properly validate frame length parameters, causing the kernel to attempt memory operations with invalid or negative values. When the kernel processes the malformed frame, it calculates buffer sizes and offsets based on the corrupted SKB length, leading to memory corruption that ultimately results in kernel panic or system crash. The IEEE 802.11 wireless protocol implementation in the Linux kernel fails to properly validate input parameters, particularly when handling Quality of Service data frames that have been crafted to exploit this specific arithmetic boundary condition.
From an operational perspective, this vulnerability presents a significant risk to wireless network infrastructure and devices running affected Linux kernel versions. Attackers can remotely trigger system crashes by transmitting specially crafted wireless frames to any device that processes IEEE 802.11 traffic, including routers, access points, and wireless network interfaces. The impact extends beyond simple service disruption as the kernel panic can cause complete system shutdown, potentially affecting network availability for legitimate users and creating opportunities for more sophisticated attacks. The vulnerability affects systems where wireless networking is enabled and actively processing frames, making it particularly dangerous in enterprise environments, public wireless networks, and any deployment where wireless access points are exposed to untrusted networks. The remote nature of the attack means that adversaries do not require physical access or network proximity to exploit the vulnerability, significantly expanding the attack surface.
Mitigation strategies for CVE-2007-4997 primarily focus on immediate kernel version upgrades to 2.6.23 or later, which contain the necessary patches to address the integer underflow condition. System administrators should prioritize updating wireless networking components and ensuring all kernel versions are current with security patches. Additional protective measures include implementing wireless network monitoring to detect anomalous frame patterns and deploying intrusion detection systems that can identify and block suspicious wireless traffic. Network segmentation and access control measures can help limit the potential impact of such attacks by isolating wireless networks and reducing the attack surface. Organizations should also consider implementing network-wide wireless frame validation and filtering mechanisms that can detect and drop malformed frames before they reach the kernel's wireless processing subsystem. The vulnerability demonstrates the importance of proper input validation in kernel space code and highlights the critical need for rigorous security testing of network protocol implementations, particularly those handling untrusted external data. This vulnerability aligns with ATT&CK technique T1499.002 for network denial of service and represents a classic example of how seemingly minor arithmetic errors in kernel code can result in catastrophic system failures.