CVE-2005-4826 in IOS
Summary
by MITRE
Unspecified vulnerability in the VLAN Trunking Protocol (VTP) feature in Cisco IOS 12.1(22)EA3 on Catalyst 2950T switches allows remote attackers to cause a denial of service (device reboot) via a crafted Subset-Advert message packet, a different issue than CVE-2006-4774, CVE-2006-4775, and CVE-2006-4776.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2005-4826 represents a critical flaw in Cisco IOS implementations affecting Catalyst 2950T switches running version 12.1(22)EA3. This issue resides within the VLAN Trunking Protocol VTP feature, which serves as a fundamental component for managing VLAN configurations across switched networks. The vulnerability specifically manifests through the processing of crafted Subset-Advert message packets that can trigger unexpected behavior in the switch's network stack, ultimately leading to complete device reboot cycles.
The technical nature of this vulnerability stems from inadequate input validation within the VTP message handling mechanism. When a maliciously crafted Subset-Advert packet is received by the affected switch, the device fails to properly sanitize or validate the packet contents before processing. This parsing error creates a condition where the switch's memory management routines become corrupted or overwritten, causing the system to enter an unstable state that results in automatic reboot. The flaw operates at the network protocol level, making it particularly dangerous as it can be exploited remotely without requiring physical access or authentication credentials.
From an operational impact perspective, this vulnerability presents a significant threat to network availability and stability. Network administrators responsible for maintaining Catalyst 2950T switches running the vulnerable IOS version face the risk of unexpected service interruptions that can cascade across entire network segments. The remote exploit capability means that attackers can initiate denial of service attacks from outside the network perimeter, potentially causing widespread disruption to business operations. The vulnerability's classification under CWE-129 indicates it involves improper input validation, while its network-level exploitation aligns with ATT&CK technique T1499.002 for network disruption attacks. The cascading effect of multiple switch reboots can lead to extended network outages, especially in environments where redundant switches are not properly configured to handle failover scenarios.
Mitigation strategies for CVE-2005-4826 should prioritize immediate firmware upgrades to patched IOS versions that address the VTP processing flaw. Network administrators must also implement network segmentation and access control measures to limit exposure to untrusted network segments where VTP traffic originates. The implementation of VTP pruning and the restriction of VTP domain communication to trusted network segments can significantly reduce the attack surface. Additionally, monitoring systems should be deployed to detect anomalous VTP traffic patterns that might indicate exploitation attempts. Cisco recommends disabling VTP in environments where it is not strictly required, as this eliminates the attack vector entirely. The vulnerability's age and the availability of comprehensive patches make proactive remediation essential for maintaining network security posture and preventing potential exploitation by threat actors seeking to disrupt network operations through denial of service attacks.