CVE-2005-3426 in Content Services Switch
Summary
by MITRE
Cisco CSS 11500 Content Services Switch (CSS) with SSL termination services allows remote attackers to cause a denial of service (memory corruption and device reload) via a malformed client certificate during SSL session negotiation.
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Analysis
by VulDB Data Team • 06/29/2025
The Cisco CSS 11500 Content Services Switch represents a critical network infrastructure device designed to handle SSL termination services for secure web traffic. This appliance operates as a layer 4-7 load balancer and content switching device that processes encrypted traffic between clients and servers. When configured with SSL termination capabilities, the CSS 11500 acts as an intermediary that decrypts incoming SSL connections, processes the traffic, and then re-encrypts it for transmission to backend servers. The device's role in SSL session negotiation makes it a prime target for attackers seeking to disrupt network services through memory corruption vulnerabilities.
The vulnerability stems from insufficient input validation during SSL session negotiation when processing client certificates. Specifically, the CSS 11500 fails to properly validate the structure and content of malformed client certificates presented during the SSL handshake process. When an attacker submits a specially crafted malformed certificate, the device's SSL processing engine encounters memory corruption issues that lead to system instability. This flaw exists within the certificate parsing logic where the device does not adequately sanitize certificate fields or enforce proper bounds checking on certificate data structures. The vulnerability manifests as a buffer overflow condition or improper memory allocation when the device attempts to process the malformed certificate data, causing the system to crash and subsequently reload.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential business continuity issues and security implications. Remote attackers can exploit this weakness without requiring authentication credentials, making it particularly dangerous in environments where the device is accessible from untrusted networks. When the device reloads due to memory corruption, it results in complete service interruption for all SSL-terminated applications that depend on the CSS 11500. Network administrators may experience extended downtime while the device restarts and re-establishes SSL session states, potentially affecting multiple applications and services. The vulnerability also represents a potential entry point for more sophisticated attacks, as the device reload process could provide opportunities for additional exploitation attempts or denial of service cascading effects.
Mitigation strategies for this vulnerability should encompass both immediate and long-term defensive measures. The most effective immediate solution involves applying the official Cisco security patches and software updates that address the specific SSL certificate validation flaw. Network administrators should also implement network segmentation to limit access to the CSS 11500 device to trusted sources only, reducing the attack surface for remote exploitation attempts. Additional defensive measures include implementing SSL inspection policies that validate certificate formats before they reach the device, deploying intrusion detection systems that monitor for malformed certificate traffic patterns, and establishing monitoring protocols to detect device reload events. Organizations should also consider implementing redundant SSL termination services to minimize the impact of potential exploitation attempts and maintain service availability during patch deployment cycles.
This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation in security-critical network infrastructure components. From an attack perspective, it maps to ATT&CK technique T1499.004 for network denial of service, demonstrating how vulnerabilities in SSL processing can be leveraged for service disruption. The attack vector involves a simple network-based approach where an attacker sends a malformed client certificate to the device, making it particularly difficult to detect and prevent through traditional network monitoring alone. The vulnerability highlights the importance of validating all inputs in network security appliances and demonstrates how seemingly minor validation flaws can lead to complete system compromise and service disruption.