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A critical vulnerability, identified as CVE-2026-20349, has been discovered in the Remote Access SSL VPN service of Cisco Secure Firewall Threat Defense (FTD) Software. This flaw is rooted in improper error checking when the system processes HTTP requests. An unauthenticated, remote attacker can exploit this weakness by sending a specially crafted HTTP request to the affected device. The vulnerability stems from an “Improper Clearing of Heap Memory Before Release” (CWE-244), leading to a denial-of-service (DoS) condition. If successfully exploited, the attack causes the device to reload unexpectedly, thereby disrupting network operations and resulting in a loss of availability. This vulnerability carries a CVSS v3.1 base score of 8.6 out of 10, classifying it as a high-severity threat. Critically, this vulnerability is being actively exploited in the wild, underscoring the urgent need for remediation. Affected products include Cisco Secure Firewall ASA and FTD Software running specific versions where the Remote Access SSL VPN service is enabled.
DailyCVE Form:
Platform: Cisco FTD
Version: 7.0, 7.2, 7.4, 7.6, 7.7
Vulnerability: Remote DoS
Severity: High (8.6)
date: August 11, 2026
Prediction: Patch already available
What Undercode Say:
Analytics on this CVE show active exploitation in the wild. The vulnerability is being leveraged to cause unexpected device reloads, leading to a denial-of-service condition. Immediate patching is strongly advised.
Exploit: (Educational Purposes!)
Crafted HTTP request to trigger the vulnerability curl -X GET "https://<target-ip>/vpn/..." -H "Host: <target-ip>" -H "Connection: Keep-Alive" ...
Example of a malicious packet that could cause a reload This is a representation and not a functional exploit
Protection:
- Apply the latest security updates provided by Cisco immediately.
- There are no known workarounds for this vulnerability.
- Restrict access to the SSL VPN service to trusted networks where possible.
Impact:
- Unexpected reload of the affected Cisco Secure Firewall device.
- Denial of service (DoS) condition, causing network disruption.
- Potential for significant operational downtime while the device restarts.
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Sources:
Reported By: nvd.nist.gov
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