Secure Firewall ASA and FTD

CVE-2024-20526: A vulnerability in the SSH server of Cisco Adaptive Security Appliance (ASA) Software could allow an unauth…

A vulnerability in the SSH server of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition for the SSH server of an affected device.

Published

ExploitedNot in CISA KEV
Ransomware useNot reportedPer CISA
SeverityMEDIUMCVSS 3.1 5.3
EPSS0.49%Chance of exploitation in 30 days
Public exploitNot tracked
FixNot yet

Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.

Affected and fixed versions

Product / branchFixed in
Cisco Adaptive Security Appliance (ASA) Software 9.16See the advisory
Cisco Adaptive Security Appliance (ASA) Software 9.16See the advisory
Cisco Adaptive Security Appliance (ASA) Software 9.18See the advisory
Cisco Adaptive Security Appliance (ASA) Software 9.20See the advisory

Always confirm against the vendor advisory, which lists every fixed hotfix.

What it is

A vulnerability in the SSH server of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition for the SSH server of an affected device. This vulnerability is due to a logic error when an SSH session is established. An attacker could exploit this vulnerability by sending crafted SSH messages to an affected device. A successful exploit could allow the attacker to exhaust available SSH resources on the affected device so that new SSH connections to the device are denied, resulting in a DoS condition. Existing SSH connections to the device would continue to function normally. The device must be rebooted manually to recover. However, user traffic would not be impacted and could be managed using a remote application such as Cisco Adaptive Security Device Manager (ASDM).

Exploitation

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

Sources

KEV status, EPSS score and vendor data refreshed automatically, last on 11 Oct 2026.

Get alerts

A notification when we publish a new analysis or a covered vendor gets a new actively exploited CVE. No account, no email.