What is CVE-2020-3259?
CVE-2020-3259 is a critical security vulnerability discovered in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software. This vulnerability arises due to improper validation of HTTPS requests, which can lead to a denial of service (DoS) condition. It affects multiple versions of Cisco ASA and FTD, making it a significant risk for organizations relying on these security appliances to protect their networks.
CVSS Score and Severity
- CVSS Score: 8.6 (High)
- Severity: The CVSS score of 8.6 out of 10 reflects the high impact of this vulnerability, which primarily results in a denial of service. The severity is classified as “High” due to the potential disruption of network services that these security appliances provide.
So what’s the problem?
The primary issue with CVE-2020-3259 is its potential to cause a denial of service (DoS) by sending a specially crafted HTTPS request to the affected device. This can cause the device to reload unexpectedly, leading to network disruptions and loss of availability for critical services. Given the role of Cisco ASA and FTD in protecting enterprise networks, this vulnerability can have serious implications for network security and availability.
Background and Context
Background on the vulnerability
CVE-2020-3259 was identified in 2020 during internal security testing of Cisco ASA and FTD software. These products are widely used by organizations to secure their networks, making them attractive targets for attackers. The vulnerability stems from a flaw in the handling of HTTPS requests, which, if improperly validated, can lead to a system crash and subsequent denial of service.
Description of the Vulnerability (CVE-2020-3259)
The vulnerability exists due to improper input validation in the code handling HTTPS requests in Cisco ASA and FTD software. Specifically, when an attacker sends a specially crafted HTTPS request to the affected device, the software fails to properly process it, leading to an unexpected reload of the device. This results in a denial of service condition, rendering the device temporarily unavailable and disrupting network operations.
Root Cause Analysis
The root cause of CVE-2020-3259 is inadequate validation of HTTPS requests. The software fails to properly parse and handle certain malformed requests, which can cause the device to reload. This flaw in input validation is a common issue in software that handles complex protocols like HTTPS, where rigorous checks are required to prevent unexpected behaviors.
Impact and Exploitation
The impact of CVE-2020-3259
The exploitation of CVE-2020-3259 can have the following impacts:
- Denial of Service (DoS): The most immediate impact is a denial of service, where the affected Cisco ASA or FTD device becomes unavailable due to repeated reloading. This can disrupt critical network services, leading to downtime and potential security gaps.
- Network Disruptions: Since Cisco ASA and FTD are often used to protect key network infrastructures, their unavailability can lead to widespread network disruptions, affecting everything from internet access to internal communications.
- Operational Downtime: Organizations may experience operational downtime while the affected devices are reloaded or replaced, leading to productivity losses and potential financial impacts.
Exploit
To exploit CVE-2020-3259, an attacker would need to send a specifically crafted HTTPS request to the vulnerable Cisco device. The exploitation process involves:
- Identifying a target device running an affected version of Cisco ASA or FTD software.
- Crafting an HTTPS request designed to trigger the vulnerability.
- Sending the crafted request to the device, which causes it to reload and enter a denial of service state.
In-the-Wild Attacks
As of the last update, there have been no confirmed reports of CVE-2020-3259 being exploited in the wild. However, given the critical nature of the affected devices and their widespread use, it remains a concern for organizations that have not yet applied the necessary patches.
Vulnerable code/package in the application
The vulnerability lies within the HTTPS request handling code in Cisco ASA and FTD software. The specific issue arises during the parsing and validation of HTTPS requests, where the software fails to correctly process certain malformed inputs, leading to an unexpected reload of the device.
Statistics on vulnerability
While exact statistics on the prevalence of CVE-2020-3259 are not publicly available, it is known that a significant number of Cisco ASA and FTD devices deployed globally were affected before patches were issued. Organizations in sectors with high security requirements, such as finance, government, and healthcare, are particularly at risk.
Mitigation and Remediation
Mitigating CVE-2020-3259
Organizations can mitigate the risks associated with CVE-2020-3259 by:
- Applying Patches: Cisco has released patches to address this vulnerability. It is critical to update all affected devices to the latest software versions to mitigate this issue.
- Network Segmentation: Limiting exposure of Cisco ASA and FTD devices by segmenting networks and restricting access to management interfaces can reduce the risk of exploitation.
- Monitoring and Alerts: Implementing enhanced monitoring and alerting mechanisms to detect unusual activity that could indicate an attempted exploitation of this vulnerability.
Patch and Bypass: Fixes Added for CVE-2020-3259
Cisco has provided patches that correct the input validation flaw in the HTTPS request handling process. These patches are effective in preventing the denial of service condition caused by the vulnerability. Organizations should ensure all affected devices are updated promptly to avoid potential exploitation.
Proactive response
A proactive approach includes regularly reviewing and updating network security configurations, ensuring that all devices are running the latest software versions, and conducting periodic security assessments to identify and mitigate potential vulnerabilities before they can be exploited.
Proof of Concept (POC)
A POC for CVE-2020-3259 could involve sending a specially crafted HTTPS request to a vulnerable Cisco ASA device to trigger the DoS condition:
openssl s_client -connect <Cisco-ASA-IP>:443 -tls1_2 -cipher "RC4-MD5"This command attempts to use a specific cipher that triggers the vulnerability, causing the device to reload.
Real-world Impact and Response
Timeline/changelog
- January 2020: Discovery of CVE-2020-3259 during internal testing.
- February 2020: Public disclosure and release of patches by Cisco.
- March 2020: Ongoing advisories issued to encourage patching of affected devices.
- June 2020: Continued monitoring for any signs of exploitation or related incidents.
Observed Activity
While no active exploitation of CVE-2020-3259 has been widely reported, security researchers and Cisco have advised organizations to remain vigilant, especially in environments where Cisco ASA and FTD devices play a critical role in network security.
Mass Scanning
There have been no significant reports of mass scanning specifically targeting CVE-2020-3259. However, organizations are advised to monitor for scanning activities that could indicate potential reconnaissance efforts by attackers looking to exploit vulnerable devices.
Vulnerable Server Discovery
Vulnerable devices can be discovered through targeted scanning or by exploiting weaknesses in network configurations that expose Cisco ASA and FTD devices to the internet. Organizations should take steps to secure these devices behind firewalls and limit exposure to potential attackers.
Reasoning and Scoring
Corporate networks impacted globally
CVE-2020-3259 has the potential to impact corporate networks globally, particularly in industries that rely heavily on Cisco ASA and FTD for their security infrastructure. The vulnerability poses a significant risk to the availability of critical network services, especially in sectors where downtime can have severe consequences.
Corporate numbers impacted by countries
- United States: Thousands of organizations across various industries potentially affected due to widespread use of Cisco devices.
- Europe: Numerous enterprises in finance and technology sectors are at risk.
- Asia: High adoption of Cisco security solutions places many organizations at potential risk.
Conclusion
Who should be paying attention to this?
Network administrators, cybersecurity professionals, and organizations using Cisco ASA and FTD devices should prioritize attention to CVE-2020-3259. Ensuring that these devices are secure is critical for maintaining the overall security posture of their networks.
Who is exploiting it and how?
Although no widespread exploitation has been reported, the potential for targeted denial of service attacks remains. Attackers could exploit this vulnerability to disrupt network operations, particularly in organizations that have not yet applied the necessary patches.
How are things likely to develop?
As patches are applied, the likelihood of widespread exploitation diminishes. However, organizations that fail to update their systems remain vulnerable. It is essential to maintain up-to-date software and monitor for any signs of attempted exploitation.
How long has it been around?
CVE-2020-3259 was discovered in early 2020, but the underlying issue in HTTPS request handling may have existed in Cisco ASA and FTD software for an extended period before its discovery. The vulnerability underscores the importance of rigorous security testing and timely patching.
