CVE-2011-2723 in Linux
Summary
by MITRE
The skb_gro_header_slow function in include/linux/netdevice.h in the Linux kernel before 2.6.39.4, when Generic Receive Offload (GRO) is enabled, resets certain fields in incorrect situations, which allows remote attackers to cause a denial of service (system crash) via crafted network traffic.
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Analysis
by VulDB Data Team • 08/06/2024
The vulnerability identified as CVE-2011-2723 represents a critical flaw in the Linux kernel's network stack implementation that specifically affects systems running kernel versions prior to 2.6.39.4. This issue resides within the skb_gro_header_slow function located in the include/linux/netdevice.h file, which is responsible for handling Generic Receive Offload operations. The vulnerability manifests when GRO is enabled on network interfaces, creating a condition where certain network packet header fields are incorrectly reset during the packet processing pipeline. The flaw is particularly dangerous because it can be exploited remotely through carefully crafted network traffic that triggers the problematic code path. This vulnerability falls under the category of denial of service attacks, where successful exploitation results in complete system crashes and requires manual intervention to restore normal operation.
The technical root cause of this vulnerability stems from improper field management within the packet processing logic when Generic Receive Offload is active. When network packets arrive and are processed through the GRO mechanism, the skb_gro_header_slow function attempts to optimize packet handling by aggregating multiple small packets into larger ones. However, during this optimization process, the function incorrectly resets certain packet header fields that should remain intact. This mismanagement occurs specifically in scenarios where packet headers contain information that must be preserved across the GRO processing cycle. The vulnerability is classified as a buffer overflow condition according to CWE-121 and represents a memory safety issue that can be triggered through network input validation failures. The flaw demonstrates characteristics of improper input validation and memory management errors that are commonly exploited in network-based attack vectors.
The operational impact of CVE-2011-2723 extends beyond simple system crashes to encompass complete network service disruption and potential availability violations for affected systems. Any Linux system with GRO enabled and running a vulnerable kernel version becomes susceptible to this attack, making it particularly dangerous for servers, network appliances, and infrastructure devices that rely heavily on network throughput optimization. The attack requires minimal privileges and can be executed remotely, making it highly attractive to malicious actors seeking to disrupt services. Systems that process high volumes of network traffic are at increased risk, as the vulnerability can be triggered through normal network operations rather than requiring special conditions. This vulnerability directly impacts the availability aspect of the CIA triad and can be categorized under the ATT&CK technique T1499.004 for network denial of service attacks. The crash conditions can occur repeatedly, potentially leading to sustained service disruption and requiring system restarts to restore normal operations.
Mitigation strategies for CVE-2011-2723 focus primarily on kernel version upgrades to 2.6.39.4 or later, which contain the necessary patches to correct the field reset logic in the skb_gro_header_slow function. Organizations should prioritize immediate deployment of updated kernel versions across their infrastructure to eliminate exposure to this vulnerability. Alternative mitigations include disabling Generic Receive Offload on affected systems, though this approach reduces network performance and throughput optimization benefits. System administrators should also implement network monitoring solutions to detect anomalous traffic patterns that might indicate exploitation attempts. The vulnerability highlights the importance of maintaining current kernel versions and following security update schedules. Additionally, implementing network segmentation and access controls can help limit the potential impact of successful exploitation attempts, while regular security audits should verify that systems remain patched against known vulnerabilities. Organizations should also consider implementing intrusion detection systems to monitor for network traffic patterns associated with this specific vulnerability class.