CVE-2020-5135 in SonicOS
Summary
by MITRE • 10/12/2020
A buffer overflow vulnerability in SonicOS allows a remote attacker to cause Denial of Service (DoS) and potentially execute arbitrary code by sending a malicious request to the firewall. This vulnerability affected SonicOS Gen 6 version 6.5.4.7, 6.5.1.12, 6.0.5.3, SonicOSv 6.5.4.v and Gen 7 version 7.0.0.0.
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Analysis
by VulDB Data Team • 02/06/2025
The buffer overflow vulnerability identified as CVE-2020-5135 resides within SonicOS firmware, specifically impacting SonicWall firewalls across multiple generations including Gen 6 versions 6.5.4.7, 6.5.1.12, 6.0.5.3 and SonicOSv 6.5.4.v along with Gen 7 version 7.0.0.0. This vulnerability represents a critical security flaw that allows remote attackers to exploit the system through carefully crafted network requests. The flaw manifests in the handling of incoming packets that exceed predetermined buffer limits, creating conditions where memory corruption can occur. The vulnerability operates at the network protocol level where SonicWall firewalls process incoming traffic, making it particularly dangerous as it can be exploited without requiring authentication or physical access to the device. The attack vector involves sending maliciously formatted requests to the firewall's management interface or network processing components, which then triggers the buffer overflow condition. This type of vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions where insufficient boundary checking allows attackers to overwrite adjacent memory locations. The operational impact of this vulnerability extends beyond simple denial of service as it presents potential for arbitrary code execution, making it a severe threat to network security infrastructure.
The technical implementation of this buffer overflow occurs when the SonicOS firmware fails to properly validate input lengths before copying data into fixed-size buffers. Attackers can craft packets with oversized payloads that exceed the allocated buffer space, causing the system to overwrite adjacent memory regions. This memory corruption can lead to unpredictable behavior including system crashes, restarts, and in some cases, the execution of malicious code within the firewall's memory space. The vulnerability affects the firewall's ability to process legitimate network traffic while simultaneously providing an attack surface for remote exploitation. The affected versions span multiple SonicWall generations, indicating a widespread issue that required coordinated patching across different firmware architectures. The attack requires minimal privileges as it operates over the network without requiring authentication, making it particularly attractive to threat actors seeking to compromise network security infrastructure. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under the T1210 category for exploitation of remote services, where adversaries leverage software vulnerabilities to gain unauthorized access or disrupt services. The memory corruption aspect of this vulnerability also aligns with ATT&CK technique T1059 for command and control through code injection, as successful exploitation could allow attackers to execute arbitrary commands within the firewall environment.
The operational consequences of CVE-2020-5135 extend beyond immediate service disruption to potentially provide attackers with persistent access to network infrastructure. When exploited successfully, this vulnerability can result in complete firewall compromise, allowing attackers to bypass network security controls and potentially access internal network resources. The DoS aspect of the vulnerability can be used to deny legitimate users access to network services while the code execution capability provides a pathway for more sophisticated attacks including data exfiltration or lateral movement within the network. Organizations running affected SonicWall firmware versions face significant risk as the vulnerability can be exploited remotely without detection, potentially remaining undetected for extended periods. The impact on network security operations is substantial as firewalls serve as critical boundary protection devices, and their compromise can undermine the entire security posture of an organization. The vulnerability affects not only the availability of network services but also the integrity of the security controls that organizations rely upon for network protection. This represents a fundamental failure in the security architecture of SonicWall devices, where basic input validation mechanisms were insufficient to prevent memory corruption. The widespread nature of affected versions indicates that organizations across multiple sectors and geographies may be at risk, requiring urgent patching and security assessments.
Organizations should immediately implement mitigation strategies including applying the vendor-provided security patches for all affected SonicWall firmware versions to address the buffer overflow vulnerability. Network administrators must also consider implementing network segmentation and access controls to limit exposure of SonicWall firewalls to untrusted networks. Monitoring network traffic for suspicious patterns that may indicate exploitation attempts should be part of the security operations routine. The firewall configuration should be reviewed to ensure that only necessary services are exposed to external networks and that administrative access is restricted to trusted sources. Additional defensive measures include implementing intrusion detection systems that can identify potential exploitation attempts and configuring logging to capture relevant network events. Organizations should also conduct comprehensive vulnerability assessments to identify any other potential security flaws in their network infrastructure. The patching process must be carefully planned to avoid service disruption while ensuring all affected devices receive updates. Security teams should establish incident response procedures specifically for firewall compromise scenarios and maintain updated threat intelligence feeds to monitor for related exploitation attempts. Regular security audits and penetration testing should be conducted to validate the effectiveness of implemented security controls and identify any remaining vulnerabilities in the network security infrastructure.