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PatchSiren cyber security CVE debrief

CVE-2026-20106 Cisco CVE debrief

A vulnerability in the Remote Access SSL VPN, HTTP management and MUS functionality, of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to exhaust device memory resulting in a denial of service (DoS) condition requiring a manual reboot. This vulnerability is due to trusting user input without validation. An attacker could exploit this vulnerability by sending crafted packets to the Remote Access SSL VPN server. A successful exploit could allow the attacker to cause the device to stop responding, resulting in a DoS condition.

Vendor
Cisco
Product
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-04
Original CVE updated
2026-08-11
Advisory published
2026-03-04
Advisory updated
2026-08-11

Who should care

Organizations using Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software should review and apply patches to mitigate this vulnerability. Security teams and network administrators are particularly advised to take immediate action.

Technical summary

The vulnerability in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software allows for a potential DoS condition due to improper validation of user input. This could allow an unauthenticated, remote attacker to cause the device to stop responding, necessitating a manual reboot. The CVSS score for this vulnerability is 5.3, indicating a medium severity.

Defensive priority

Medium priority given the CVSS score of 5.3 and the potential for a DoS condition.

Recommended defensive actions

  • Review and apply patches from Cisco for affected ASA and FTD software versions.
  • Implement compensating controls such as rate limiting on VPN access.
  • Monitor system logs for unusual patterns indicative of potential exploits.
  • Restrict access to Remote Access SSL VPN servers to only necessary personnel.
  • Verify and update inventory of Cisco ASA and FTD devices to ensure accurate tracking.

Evidence notes

The vulnerability is caused by trusting user input without validation, allowing an attacker to send crafted packets to the Remote Access SSL VPN server, potentially causing a DoS condition. Evidence is based on official CVE and NVD records.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-20106 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-20106

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-20106 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-20106

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.