CVE-2026-20009
Cisco Adaptive Security Appliance Software 9.17.1 – 9.18.4.71
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:NSummary
CVE-2026-20009 is a medium-severity Improper Neutralization of Special Elements (CWE-138) vulnerability in Cisco Adaptive Security Appliance Software. Its CVSS base score is 5.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 31th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9429
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.3.12
Mitigating Controls (NIST 800-53 r5) AI
Input validation enforces neutralization or rejection of special syntactic elements before they reach a downstream interpreter.
Security engineering principles include requirements for safe input handling and neutralization of control characters.
Output filtering can neutralize special elements before they are interpreted by a receiving component.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require proper neutralization of inputs to prevent injection flaws.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect instances of CWE-138 but does not itself implement the neutralization controls.
Secure development life cycle mandates input validation and sanitization that directly prevents improper neutralization of special elements.
Application security requirements explicitly call for controls against injection and malformed input that cause CWE-138.
Secure system architecture principles reduce attack surface but do not prescribe the specific neutralization techniques needed for CWE-138.
Secure coding standards require proper escaping and neutralization of special elements, directly eliminating CWE-138.