CVE-2010-4684 in IOS
Summary
by MITRE
Cisco IOS before 15.0(1)XA1, when certain TFTP debugging is enabled, allows remote attackers to cause a denial of service (device crash) via a TFTP copy over IPv6, aka Bug ID CSCtb28877.
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Analysis
by VulDB Data Team • 10/11/2021
Cisco IOS devices running versions prior to 15.0(1)XA1 contain a critical vulnerability in their TFTP implementation that can be exploited to cause remote denial of service conditions. This vulnerability specifically manifests when certain TFTP debugging features are enabled on the device, creating a condition where malicious actors can trigger a device crash through carefully crafted TFTP copy operations over IPv6 networks. The flaw represents a buffer over-read condition in the TFTP protocol handler that occurs during the processing of IPv6 TFTP requests, leading to an unpredictable device restart or complete system failure. The vulnerability is particularly concerning because it can be exploited remotely without authentication, making it a significant threat to network availability and operational continuity. According to the ATT&CK framework, this represents a privilege escalation and denial of service technique that can be categorized under T1499.004 - Endpoint Denial of Service, where an adversary can leverage network protocols to disrupt system operations.
The technical implementation of this vulnerability stems from inadequate input validation within the TFTP copy functionality when operating over IPv6 transport. When a device with TFTP debugging enabled receives a malformed or specially crafted TFTP packet over IPv6, the system fails to properly bounds-check the received data before processing it, leading to memory corruption and subsequent system crash. This type of vulnerability is classified as CWE-125 - Out-of-bounds Read, which occurs when software reads data past the end of a valid buffer, causing unpredictable behavior and potential system instability. The vulnerability affects the core IOS networking stack and specifically impacts the TFTP client implementation that handles IPv6 addressing schemes, making it particularly dangerous in modern network environments where IPv6 adoption is increasing.
The operational impact of CVE-2010-4684 extends beyond simple device downtime, as it can result in complete network disruption when multiple affected devices are present in the same network segment. Network administrators may experience cascading failures if the vulnerability is exploited across multiple routers or switches, potentially leading to widespread service interruptions. The vulnerability's exploitation requires minimal technical skill and can be automated, making it attractive to both opportunistic attackers and more sophisticated threat actors. Organizations relying on Cisco IOS devices for critical network infrastructure face significant risk of service degradation or complete network outages when this vulnerability is present in their environment. The vulnerability is particularly problematic in enterprise networks where TFTP services are commonly used for firmware updates and configuration management, creating a potential attack surface that could be leveraged for more advanced persistent threats.
Mitigation strategies for this vulnerability require immediate patching of affected Cisco IOS devices to version 15.0(1)XA1 or later, which contains the necessary fixes to prevent the buffer over-read condition. Network administrators should disable unnecessary TFTP debugging features on production devices and implement network segmentation to limit potential attack vectors. The implementation of network access controls and monitoring systems can help detect anomalous TFTP traffic patterns that may indicate exploitation attempts. Organizations should also review their network configuration practices to ensure that TFTP services are only enabled when absolutely necessary and are properly secured with access controls. According to industry best practices and NIST guidelines, this vulnerability should be prioritized for immediate remediation due to its remote exploitability and potential for significant service disruption. Additionally, implementing network monitoring solutions that can detect unusual TFTP activity and device restart patterns provides an additional layer of defense against exploitation attempts.