CVE-2011-3281 in IOS
Summary
by MITRE
Unspecified vulnerability in Cisco IOS 15.0 through 15.1, in certain HTTP Layer 7 Application Control and Inspection configurations, allows remote attackers to cause a denial of service (device reload or hang) via a crafted HTTP packet, aka Bug ID CSCto68554.
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Analysis
by VulDB Data Team • 11/23/2021
The vulnerability described in CVE-2011-3281 represents a critical denial of service flaw within Cisco IOS software versions 15.0 through 15.1 that specifically affects HTTP Layer 7 application control and inspection configurations. This issue manifests when the system processes crafted HTTP packets that exploit weaknesses in the application layer inspection mechanisms, leading to unauthorized device disruption. The vulnerability operates at the network layer where HTTP traffic is inspected and controlled, making it particularly dangerous as it can be triggered remotely without requiring authentication or elevated privileges. The bug ID CSCto68554 indicates this was tracked internally by Cisco as a significant operational concern affecting their routing and switching platforms.
The technical implementation of this vulnerability stems from improper handling of malformed HTTP packets within the application layer protocol inspection engine of Cisco IOS. When the system encounters specially crafted HTTP traffic that violates expected protocol patterns, the inspection process fails to properly validate or sanitize the input, causing the device to enter an unstable state. This typically results in either a complete device reload or a system hang that requires manual intervention to restore normal operation. The flaw demonstrates a classic buffer over-read or state management error within the HTTP inspection module, where the system does not adequately handle edge cases or malformed input sequences that should be gracefully rejected or processed without system failure.
From an operational perspective, this vulnerability poses significant risks to network availability and business continuity, particularly in enterprise environments where Cisco devices serve as core infrastructure components. Attackers can exploit this weakness to perform remote denial of service attacks against network equipment, potentially disrupting critical services, causing network outages, or creating opportunities for more sophisticated attacks. The remote nature of the exploit means that adversaries do not require physical access or network credentials to trigger the vulnerability, making it particularly attractive for cybercriminals seeking to disrupt services. Organizations with affected devices may experience unexpected downtime, increased operational overhead for system recovery, and potential financial losses due to service interruptions.
The impact of this vulnerability aligns with CWE-122, which describes buffer overflow conditions in application layer protocol handling, and can be mapped to ATT&CK technique T1499.004 for network denial of service attacks. Mitigation strategies should include immediate deployment of Cisco IOS patches and updates addressing the specific vulnerability, implementing network segmentation to limit exposure, and configuring access controls to restrict potentially malicious HTTP traffic. Organizations should also consider disabling HTTP inspection profiles when not required, implementing intrusion detection systems to monitor for suspicious HTTP traffic patterns, and maintaining comprehensive backup and recovery procedures to minimize downtime during incident response. The vulnerability underscores the importance of regular security updates and proper network configuration management to prevent exploitation of application layer inspection flaws that can compromise entire network infrastructures.