CVE-2023-20006 in ASA
Summary
by MITRE • 06/28/2023
A vulnerability in the hardware-based SSL/TLS cryptography functionality of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 2100 Series Appliances could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to an implementation error within the cryptographic functions for SSL/TLS traffic processing when they are offloaded to the hardware. An attacker could exploit this vulnerability by sending a crafted stream of SSL/TLS traffic to an affected device. A successful exploit could allow the attacker to cause an unexpected error in the hardware-based cryptography engine, which could cause the device to reload.
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Analysis
by VulDB Data Team • 08/15/2025
This vulnerability affects Cisco Adaptive Security Appliance ASA Software and Cisco Firepower Threat Defense FTD Software running on Cisco Firepower 2100 Series appliances where hardware-based SSL/TLS cryptography functionality is enabled. The flaw resides in the implementation of cryptographic functions that process SSL/TLS traffic when offloaded to dedicated hardware components. The vulnerability represents a critical design flaw in the hardware-software integration that governs secure communication processing. The affected devices operate under the assumption that hardware-based cryptographic operations will maintain stable performance regardless of input conditions, but this assumption proves incorrect when specific malformed SSL/TLS traffic patterns are processed through the hardware engine.
The technical exploitation mechanism involves sending specially crafted SSL/TLS traffic streams that trigger an implementation error within the hardware-based cryptography engine. This error manifests as an unexpected condition that forces the device to undergo an abrupt restart or reload process. The vulnerability is particularly concerning because it operates at the hardware level where cryptographic operations are offloaded from the main processing units to dedicated security chips. This offloading mechanism is designed for performance optimization but creates a surface where implementation flaws can cause complete system disruption. The error condition specifically impacts the cryptographic engine's ability to handle certain SSL/TLS protocol variations or malformed data structures that are not properly validated before processing.
From an operational impact perspective, this vulnerability creates a significant denial of service risk that can compromise network availability and security infrastructure. The device reload caused by exploitation results in complete service interruption for the affected appliance, potentially leaving network traffic unfiltered and unprotected during the restart period. This vulnerability affects organizations that rely on these security appliances for network segmentation, firewall protection, and threat detection services. The unauthenticated nature of the attack means that any remote attacker can potentially exploit this weakness without requiring prior credentials or privileged access. The DoS condition can be sustained through repeated exploitation attempts, creating prolonged service disruption that may require manual intervention to restore normal operations.
The vulnerability maps directly to CWE-119 which describes weaknesses in memory management and improper handling of resources in cryptographic implementations. It also aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through exploitation of system vulnerabilities. Organizations should implement immediate mitigations including disabling hardware-based SSL/TLS offloading if not essential for operations, applying the latest Cisco security patches, and monitoring for unusual device restart patterns. Network segmentation and redundant security appliances can provide additional protection layers. The vulnerability highlights the importance of thorough testing for hardware-software integration in security appliances and demonstrates the critical nature of maintaining updated cryptographic implementations. Regular security assessments should verify that cryptographic offloading features are properly configured and that appropriate monitoring is in place to detect exploitation attempts.