A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to ineffective memory management of the VPN web server. An attacker could exploit this vulnerability by sending a large number of crafted HTTP requests to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
With a CVSS score of 8.6, this high-severity vulnerability poses significant risks to organizations that utilize the affected Cisco software. Attackers may leverage this vulnerability to disrupt services, making it crucial for organizations to prioritize patching immediately.
Organizations should take immediate action to assess their exposure and apply necessary updates to prevent potential exploitation.
Vulnerability Details
The vulnerability described as CVE-2026-20039 affects Cisco's Secure Firewall ASA and FTD software, specifically impacting the VPN web server. The detailed CVE description clarifies that the root cause is linked to ineffective memory management. The vulnerability could allow attackers to send numerous crafted HTTP requests, leading to a denial of service by forcing the affected devices to restart.
This vulnerability is classified under CWE-244, indicating improper handling of system resources, which directly leads to availability impacts. The CVSS v3.1 vector for this vulnerability is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H, reflecting a high availability impact score.
Technical Analysis
The root cause of this vulnerability lies in the VPN web server's memory management. An attacker with network access can exploit this vulnerability with low complexity, requiring no privileges or user interaction. The attack vector is network-based, and successful exploitation can lead to a complete denial of service, making the affected devices unavailable.
The attack complexity is considered low, as the attacker does not need to possess special privileges or interact with users. The implications extend to the availability of devices, which can be significantly affected due to the potential for repeated reboots.
Risk & Impact Analysis
Risk to organizations includes potential service disruptions and loss of availability of critical network infrastructure. The blast radius for this vulnerability could affect all devices running the software versions specified, leading to a wider impact across organizational networks.
Given the CVSS score of 8.6, this vulnerability should be treated with high urgency. Organizations should address this vulnerability in their priority patch cycle, considering the potential for significant service interruption if left unpatched.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Affected versions include Cisco Secure Firewall Adaptive Security Appliance Software versions from 9.12.1 to 9.16.4.84 (exclusive), and versions from 9.17.1 to 9.18.4.57 (exclusive), as well as versions from 9.19.1 to 9.20.3.16 (exclusive), and versions from 9.22.1.1 to 9.22.2.4 (exclusive), and 9.23.1 to 9.23.1.3 (exclusive). For the Firepower Threat Defense Software, versions from 6.4.0 to 7.0.9 (exclusive), from 7.1.0 to 7.2.10 (exclusive), from 7.3.0 to 7.4.3 (exclusive), from 7.6.0 to 7.6.1 (exclusive), and from 7.7.0 to 7.7.10 (exclusive) are also vulnerable.
Mitigation & Remediation
Organizations should prioritize patching immediately. Ensure that any affected Cisco Secure Firewall ASA and FTD Software is updated to the latest versions that are not vulnerable to this issue. If patches are not immediately available, administrators should consider implementing network controls to limit access to the affected services.
For further assessment and validation of remediation, organizations may consider engaging in penetration testing to identify any remaining vulnerabilities.
Detection Guidance
Monitoring logs for unusual patterns related to HTTP request spikes or unusual reboots of the firewall devices can provide early detection of potential exploitation attempts. Security teams should be alert to behavioral anomalies that could indicate exploitation.
AppSecure Threat Intelligence Insight
The long-term significance of this vulnerability is a reminder of the importance of robust memory management in network devices. Security teams should adopt proactive measures to identify and mitigate similar vulnerabilities through regular assessments and updates.
This incident highlights trends in network vulnerabilities and the need for organizations to remain vigilant against denial of service threats. For further reading on best practices, organizations can refer to resources on penetration testing methodology and vulnerability management programs to enhance their security posture.
Organizations are encouraged to integrate regular updates and security checks into their operational procedures to maintain resilience against such vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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