Adaptive Security Appliance SoftwareOperating system · Cisco
CVE-2026-20009
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA vulnerability in Cisco ASA's proprietary SSH stack allows unauthenticated remote attackers to bypass key-based authentication. By submitting crafted input during SSH authentication, an attacker with a valid username and corresponding public key (but NOT the private key) can log in and execute commands as that user. This is due to insufficient validation of user input in the authentication phase.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Adaptive Security Appliance SoftwareOperating system
>= 9.17.1, < 9.18.4.71>= 9.19.1, < 9.20.4.10>= 9.22.1.1, < 9.22.2.14>= 9.23.1, < 9.23.1.19CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check ASA software versionExecute 'show version' on the ASA CLI or retrieve the version via SNMP/management interface. Look for the 'Cisco Adaptive Security Appliance Software' version number.Affected if The installed version falls within one of these ranges: >= 9.17.1 and < 9.18.4.71; >= 9.19.1 and < 9.20.4.10; >= 9.22.1.1 and < 9.22.2.14; >= 9.23.1 and < 9.23.1.19
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Verify SSH is enabledExecute 'show running-config | include ssh' or 'show ssh' on the ASA CLI. This displays whether SSH access is currently enabled on the device.Affected if SSH is enabled on any interface (management or outside/inside interfaces)
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Confirm SSH key-based authentication is configuredExecute 'show running-config | include crypto' or check 'aaa authentication ssh console' configuration. Look for RSA key pairs under 'crypto key generate' and SSH user entries with 'server-authentication' settings.Affected if SSH is configured with public key authentication (RSA/DSA/ECDSA keys) for any user account
The device is affected if it runs a vulnerable ASA version listed above, SSH is enabled, and SSH key-based authentication is configured for user access.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped9.18.4.719.20.4.109.22.2.14
Apply Cisco-provided patches when available; if no patch exists, consider disabling SSH access, implementing network-based access controls, or using alternative administrative access methods until a fix is released.
Upgrade to 9.23.1.19 (or the appropriate fixed version for your branch: 9.18.4.71, 9.20.4.10, or 9.22.2.14)
- 1. Identify the current ASA software version by running 'show version' in privileged EXEC mode
- 2. Determine which version range your current software falls into (9.17.1-9.18.x, 9.19.1-9.20.x, 9.22.1.1-9.22.x, or 9.23.1)
- 3. Download the appropriate fixed ASA software version from Cisco's download center: 9.18.4.71, 9.20.4.10, 9.22.2.14, or 9.23.1.19
- 4. Back up the current ASA configuration using 'write memory' or 'copy startup-config tftp:
- 5. Upload the new ASA software image to the device flash storage
- 6. Reload the device with the new image using 'reload' command
- 7. After reload, verify the new version is running with 'show version'
- 8. Test SSH authentication to confirm the vulnerability is remediated
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Adaptive Security Appliance Software
Scoped from the published advisory
- Consultation4.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,304.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20009 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-20009 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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