CVE-2009-5038 in IOS
Summary
by MITRE
Cisco IOS before 15.0(1)XA does not properly handle IRC traffic during a specific time period after an initial reload, which allows remote attackers to cause a denial of service (device reload) via an attempted connection to a certain IRC server, related to a "corrupted magic value," aka Bug ID CSCso05336.
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Analysis
by VulDB Data Team • 10/11/2021
Cisco IOS versions prior to 15.0(1)XA contain a critical vulnerability in their IRC protocol handling mechanism that can be exploited to trigger unauthorized device reloads. This flaw manifests during a specific temporal window following a device reboot when the system processes IRC traffic, creating an exploitable condition that remote attackers can leverage for denial of service attacks. The vulnerability stems from improper handling of IRC protocol magic values, which are essential data structures used to identify and validate protocol connections. When an attacker establishes a connection to a specific IRC server during this vulnerable time period, the corrupted magic value causes the IOS kernel to malfunction and subsequently restart the device. This behavior aligns with CWE-248, which addresses improper exception handling in software systems, and represents a classic example of an uninitialized variable or memory corruption issue that leads to system instability. The vulnerability specifically affects Cisco IOS implementations where the IRC protocol parser fails to properly validate incoming connection parameters, particularly during the device initialization phase. Attackers can exploit this weakness by simply connecting to a designated IRC server, making the attack vector extremely accessible and requiring no specialized knowledge or equipment. The timing aspect of this vulnerability is crucial as it only remains exploitable during a brief period after device reload, typically measured in minutes, which makes it challenging to detect and prevent without proper monitoring. This issue directly impacts network availability and operational continuity, as unauthorized device reboots can disrupt critical network services and potentially provide attackers with opportunities to establish persistent access points within the network infrastructure. The vulnerability demonstrates a fundamental flaw in the IOS protocol stack implementation where proper state management and validation procedures are not adequately enforced during device boot cycles. From an operational security perspective, this vulnerability represents a significant risk to network availability as it allows remote attackers to cause complete service disruption through simple network connections. The exploit requires minimal resources and can be executed from any location with network access to the vulnerable device, making it particularly dangerous in enterprise and service provider environments where network uptime is critical. Organizations running affected IOS versions should prioritize immediate patching and implementation of network segmentation controls to limit exposure. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service tactics, as it allows attackers to gain unauthorized control over device operations and disrupt network services. This particular bug highlights the importance of thorough protocol validation and proper initialization procedures in network operating systems, as inadequate handling of network protocol states can lead to severe operational impacts. The vulnerability also underscores the need for comprehensive testing procedures during software development and release cycles, particularly for protocol implementations that handle external connections. Security professionals should implement network monitoring solutions to detect unusual connection patterns to IRC servers and establish proper access controls to limit which devices can connect to external IRC services. The issue demonstrates how seemingly minor protocol handling errors can result in major operational disruptions and emphasizes the critical nature of maintaining up-to-date network device firmware and security patches.