Cisco Secure Firewall Adaptive Security Appliance Software SSH Stack special element

Summaryinfo

A vulnerability classified as problematic was found in Cisco Secure Firewall Adaptive Security Appliance Software. This affects an unknown part of the component SSH Stack. The manipulation results in special element. This vulnerability was named CVE-2026-20009. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic has been found in Cisco Secure Firewall Adaptive Security Appliance Software. Affected is an unknown function of the component SSH Stack. The manipulation with an unknown input leads to a special element vulnerability. CWE is classifying the issue as CWE-138. The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as control elements or syntactic markers when they are sent to a downstream component. This is going to have an impact on confidentiality. CVE summarizes:

A vulnerability in the implementation of the proprietary SSH stack with SSH key-based authentication in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to log in to a Cisco Secure Firewall ASA device and execute commands as a specific user. This vulnerability is due to insufficient validation of user input during the SSH authentication phase. An attacker could exploit this vulnerability by submitting crafted input during SSH authentication to an affected device. A successful exploit could allow the attacker to log in to the device as a specific user without the private SSH key of that user. To exploit this vulnerability, the attacker must possess a valid username and the associated public key. The private key is not required. Notes: Exploitation of this vulnerability does not provide the attacker with root access. The authentication, authorization, and accounting (AAA) configuration command auto-enable is not affected by this vulnerability.  

The advisory is shared for download at sec.cloudapps.cisco.com. This vulnerability is traded as CVE-2026-20009 since 10/08/2025. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 03/05/2026).

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Firewall Software

Vendor

• Cisco

Name

• Secure Firewall Adaptive Security Appliance Software

Version

• 9.17.1
• 9.17.1.7
• 9.17.1.9
• 9.17.1.10
• 9.17.1.11
• 9.17.1.13
• 9.17.1.15
• 9.17.1.20
• 9.17.1.30
• 9.17.1.33
• 9.17.1.39
• 9.17.1.45
• 9.17.1.46
• 9.18.1
• 9.18.1.3
• 9.18.2
• 9.18.2.5
• 9.18.2.7
• 9.18.2.8
• 9.18.3
• 9.18.3.39
• 9.18.3.46
• 9.18.3.53
• 9.18.3.55
• 9.18.3.56
• 9.18.4
• 9.18.4.5
• 9.18.4.8
• 9.18.4.22
• 9.18.4.24
• 9.18.4.29
• 9.18.4.34
• 9.18.4.40
• 9.18.4.47
• 9.18.4.50
• 9.18.4.52
• 9.18.4.53
• 9.18.4.57
• 9.18.4.66
• 9.18.4.67
• 9.18.4.68
• 9.19.1
• 9.19.1.5
• 9.19.1.9
• 9.19.1.12
• 9.19.1.18
• 9.19.1.22
• 9.19.1.24
• 9.19.1.27
• 9.19.1.28
• 9.19.1.31
• 9.19.1.37
• 9.19.1.38
• 9.19.1.42
• 9.20.1
• 9.20.1.5
• 9.20.2
• 9.20.2.10
• 9.20.2.21
• 9.20.2.22
• 9.20.3
• 9.20.3.4
• 9.20.3.7
• 9.20.3.9
• 9.20.3.10
• 9.20.3.13
• 9.20.3.16
• 9.20.3.20
• 9.20.4
• 9.20.4.7
• 9.22.1.1
• 9.22.1.2
• 9.22.1.3
• 9.22.1.6
• 9.22.2
• 9.22.2.4
• 9.22.2.9
• 9.22.2.13
• 9.23.1
• 9.23.1.3
• 9.23.1.7
• 9.23.1.13

License

• commercial

Website

• Vendor: https://www.cisco.com/

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