CVE-2006-4776 in IOS
Summary
by MITRE
Heap-based buffer overflow in the VLAN Trunking Protocol (VTP) feature in Cisco IOS 12.1(19) allows remote attackers to execute arbitrary code via a long VLAN name in a VTP type 2 summary advertisement.
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Analysis
by VulDB Data Team • 01/14/2025
The vulnerability described in CVE-2006-4776 represents a critical heap-based buffer overflow flaw within Cisco IOS 12.1(19) that specifically targets the VLAN Trunking Protocol implementation. This vulnerability exists in the handling of VTP type 2 summary advertisements, which are used by Cisco switches to synchronize VLAN information across a network. The flaw manifests when the system processes a maliciously crafted VLAN name that exceeds the allocated buffer size, creating conditions that enable attackers to overwrite adjacent memory locations in the heap. This type of vulnerability falls under CWE-121, heap-based buffer overflow, which is classified as a serious memory corruption issue that can lead to arbitrary code execution.
The technical exploitation of this vulnerability requires an attacker to send a specially crafted VTP type 2 summary advertisement packet containing an excessively long VLAN name to a vulnerable Cisco IOS device. When the device processes this malformed packet, the insufficient bounds checking in the VTP implementation causes the buffer overflow to occur in the heap memory region. The overflow allows attackers to overwrite critical memory structures, potentially including return addresses or function pointers, which can then be manipulated to redirect execution flow to malicious code. This attack vector operates at the network level and can be executed remotely, making it particularly dangerous in networked environments where VTP is actively used for VLAN management.
The operational impact of this vulnerability extends beyond simple code execution, as it can lead to complete compromise of network infrastructure devices. When successfully exploited, attackers gain the ability to execute arbitrary code with the privileges of the affected device, potentially allowing them to establish persistent backdoors, modify network configurations, or even take control of the entire switch or router. The vulnerability affects network availability and integrity, as compromised devices can be used to launch further attacks against other network segments or to disrupt legitimate network operations. This represents a significant threat to network security, particularly in enterprise environments where VTP is commonly deployed to manage VLAN configurations across multiple switches.
Cisco addressed this vulnerability through software updates that included proper bounds checking and input validation for VLAN names in VTP advertisements. The recommended mitigation strategy involves applying the latest security patches and updates to all affected Cisco IOS devices, while also implementing network segmentation and access controls to limit the attack surface. Organizations should also consider disabling VTP where possible, as this protocol is often unnecessary in modern network designs and introduces additional attack vectors. Network monitoring should be enhanced to detect unusual VTP traffic patterns that might indicate exploitation attempts, and security professionals should implement the principle of least privilege to minimize the impact of potential compromises. This vulnerability demonstrates the importance of secure coding practices and thorough input validation, particularly in network protocol implementations that handle untrusted data from remote sources.