CVE-2011-3593 in Red Hat
Summary
by MITRE
A certain Red Hat patch to the vlan_hwaccel_do_receive function in net/8021q/vlan_core.c in the Linux kernel 2.6.32 on Red Hat Enterprise Linux (RHEL) 6 allows remote attackers to cause a denial of service (system crash) via priority-tagged VLAN frames.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability identified as CVE-2011-3593 represents a critical denial of service flaw within the Linux kernel's virtual local area network implementation. This issue specifically targets the vlan_hwaccel_do_receive function located in the net/8021q/vlan_core.c file of the 2.6.32 kernel version shipped with Red Hat Enterprise Linux 6. The vulnerability arises from insufficient validation of priority-tagged VLAN frames, creating a scenario where maliciously crafted network traffic can trigger system instability. The flaw demonstrates characteristics consistent with a buffer over-read or improper input handling that can lead to kernel memory corruption and subsequent system crashes.
The technical implementation of this vulnerability stems from the kernel's handling of IEEE 802.1Q VLAN frames that contain priority tags. When the vlan_hwaccel_do_receive function processes these frames, it fails to properly validate the priority field within the VLAN header before attempting to process the frame data. This validation gap allows attackers to craft VLAN frames with malformed priority values that cause the kernel to access memory locations beyond the intended buffer boundaries. The vulnerability is particularly dangerous because it operates at the kernel level where such faults can immediately result in system crashes and complete service interruption. According to CWE classification, this represents a CWE-125: Out-of-bounds Read vulnerability that occurs when the kernel attempts to read data beyond the allocated buffer limits.
The operational impact of CVE-2011-3593 extends beyond simple system crashes to encompass broader network service availability concerns. Remote attackers can exploit this vulnerability without requiring authentication, making it particularly dangerous in network environments where untrusted traffic flows through systems running affected kernel versions. The denial of service condition can be triggered repeatedly, potentially allowing attackers to maintain persistent disruption of network services. This vulnerability directly maps to ATT&CK technique T1499.004 which involves network denial of service attacks targeting system availability. The impact is particularly severe in enterprise environments where network infrastructure reliability is paramount, as a successful exploitation can compromise entire network segments and potentially disrupt business operations.
Mitigation strategies for CVE-2011-3593 primarily focus on applying the official Red Hat security patches that address the validation gap in the vlan_hwaccel_do_receive function. Organizations should prioritize immediate deployment of the patched kernel versions, specifically the RHEL 6 updates that contain the corrected implementation of VLAN frame processing. Network administrators should also consider implementing network segmentation and access control measures to limit exposure to potentially malicious traffic. Additionally, monitoring systems should be configured to detect unusual patterns of VLAN frame processing that might indicate exploitation attempts. The vulnerability highlights the importance of proper input validation in kernel space code and reinforces the necessity of comprehensive testing for network protocol implementations. Organizations should also consider implementing intrusion detection systems that can identify malformed VLAN frames and alert administrators to potential exploitation attempts.