CVE-2004-1464 in IOS
Summary
by MITRE
Cisco IOS 12.2(15) and earlier allows remote attackers to cause a denial of service (refused VTY (virtual terminal) connections), via a crafted TCP connection to the Telnet or reverse Telnet port.
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Analysis
by VulDB Data Team • 04/22/2026
The vulnerability identified as CVE-2004-1464 represents a significant denial of service weakness in Cisco IOS versions 12.2(15) and earlier releases. This flaw specifically targets the virtual terminal (VTY) subsystem that manages remote access connections to network devices through Telnet and reverse Telnet protocols. The vulnerability arises from insufficient input validation and connection handling mechanisms within the IOS operating system, creating an exploitable condition that can be leveraged by remote attackers to disrupt legitimate administrative access to network infrastructure.
The technical implementation of this vulnerability involves crafting malicious TCP connections to the targeted Telnet or reverse Telnet ports, which triggers unexpected behavior in the IOS VTY processing logic. When the system receives these specially crafted connection attempts, it fails to properly handle the connection states, leading to a cascade of errors that ultimately prevents legitimate VTY sessions from being established. This occurs because the IOS software does not adequately validate or sanitize incoming TCP connection parameters, allowing malformed connection requests to bypass normal session establishment procedures and cause the system to enter an inconsistent state.
The operational impact of this vulnerability extends beyond simple service disruption as it fundamentally compromises the availability of critical network management functions. Network administrators lose the ability to remotely access and configure devices through standard Telnet connections, which can severely impact network operations and maintenance activities. The vulnerability affects the core administrative capabilities of network devices, potentially leaving critical infrastructure inaccessible during security incidents or routine maintenance windows. This denial of service condition can persist until the affected device is manually rebooted or the problematic connection handling logic is patched through software updates.
From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and demonstrates characteristics consistent with attack patterns categorized under the ATT&CK framework's privilege escalation and denial of service techniques. The vulnerability represents a classic case of insufficient input sanitization that can be exploited by attackers without requiring elevated privileges, making it particularly dangerous for network infrastructure. Organizations with affected Cisco IOS versions face significant operational risks as the vulnerability can be exploited remotely, potentially allowing attackers to disrupt network services while remaining undetected in the network traffic.
Mitigation strategies for CVE-2004-1464 primarily involve applying the appropriate Cisco IOS software patches and updates that address the specific connection handling flaws. Network administrators should immediately upgrade to Cisco IOS versions that contain fixes for this vulnerability, typically those released after the initial vulnerability disclosure. Additional protective measures include implementing network access controls to restrict Telnet access to trusted administrative networks, configuring firewall rules to limit connection attempts to Telnet ports, and monitoring network traffic for suspicious connection patterns that may indicate exploitation attempts. Organizations should also consider implementing alternative secure access methods such as SSH instead of Telnet to reduce exposure to similar vulnerabilities in the future.