CVE-2008-3812 in IOS
Summary
by MITRE
Cisco IOS 12.4, when IOS firewall Application Inspection Control (AIC) with HTTP Deep Packet Inspection is enabled, allows remote attackers to cause a denial of service (device reload) via a malformed HTTP transit packet.
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Analysis
by VulDB Data Team • 05/26/2025
Cisco IOS version 12.4 contains a critical vulnerability in its Application Inspection Control module that specifically affects HTTP Deep Packet Inspection functionality. This vulnerability manifests when the firewall feature is actively enabled, creating a condition where malformed HTTP transit packets can trigger a device reload event. The flaw exists within the packet processing logic that handles HTTP traffic inspection, particularly when analyzing packets that transit through the firewall. Attackers can exploit this by crafting specially malformed HTTP packets that, when processed by the AIC module, cause the IOS operating system to crash and subsequently reload the device. The vulnerability represents a classic denial of service scenario where legitimate network operations are disrupted through intentional exploitation of the inspection mechanism.
The technical implementation of this vulnerability resides in the HTTP Deep Packet Inspection engine's handling of malformed packet structures during transit processing. When the AIC module encounters HTTP packets that do not conform to expected formatting standards, the packet parsing routine fails to properly validate or handle the irregularities, leading to an uncontrolled system state that results in device reboot. This behavior aligns with CWE-129, which addresses improper validation of input boundaries, and CWE-248, concerning exposure of an exception to an unexpected handler. The vulnerability specifically impacts the packet inspection subsystem where HTTP protocol analysis occurs, making it particularly dangerous in network environments where firewall protection is essential for security operations.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network availability and security posture. Network administrators who rely on Cisco IOS firewall functionality for traffic control and security enforcement face significant risk when this vulnerability is exploited. The device reload caused by the attack results in temporary network outages that can affect business operations and security monitoring capabilities. In enterprise environments, this could lead to cascading failures where dependent systems lose connectivity, while in mission-critical deployments, such disruptions may violate service level agreements and security compliance requirements. The vulnerability also enables attackers to perform persistent denial of service attacks that can be difficult to detect and mitigate in real-time network monitoring systems.
Mitigation strategies for this vulnerability should focus on immediate patch management and configuration adjustments. Cisco released IOS software updates that address the packet inspection flaw by improving input validation and error handling within the AIC module. Network administrators should prioritize applying these security patches to all affected devices running IOS 12.4 with enabled HTTP inspection features. Additionally, temporary configuration changes can include disabling HTTP Deep Packet Inspection when not actively required, or implementing access control lists that filter malformed traffic before it reaches the inspection engine. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, highlighting the importance of maintaining up-to-date network security controls and implementing proper monitoring to detect anomalous packet patterns that may indicate exploitation attempts.