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Cisco Adaptive Security Appliance Software SSH Server Resource Denial of Service Vulnerability

cisco-sa-asa-ssh-dos-eEDWu5RM · Medium · Published · Updated

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). Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability. This advisory is available at the following link:https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asa-ssh-dos-eEDWu5RM This advisory is part of the October 2024 release of the Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: October 2024 Semiannual Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.

Cisco advisory · CSAF JSON

Workarounds

There is no workaround for this vulnerability for devices that are running Cisco ASA Software Release 9.16.4.67 or 9.16.4.70.

For devices that are running Cisco ASA Software Release 9.18.4.40 or 9.20.3, use the ssh stack ciscossh CLI command to configure the device to use the CiscoSSH stack, which is not affected by this vulnerability. For more information about implementing this command, see the ssh stack ciscossh ["https://www.cisco.com/c/en/us/td/docs/security/asa/asa-cli-reference/S/asa-command-ref-S/so-st-commands.html#wp8411317820"] section of Cisco Secure Firewall ASA Series Command Reference.

While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

CVEsCVE-2024-20526
Cisco Bug IDsCSCwm49153
CVSS ScoreBase 5.3
Base 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:X/RL:X/RC:X
Product Names From Source
Cisco Adaptive Security Appliance (ASA) Software 9.16.4.67, Cisco Adaptive Security Appliance (ASA) Software 9.16.4.70, Cisco Adaptive Security Appliance (ASA) Software 9.18.4.40, Cisco Adaptive Security Appliance (ASA) Software 9.20.3, Cisco Secure Firewall Adaptive Security Appliance (ASA) Software, Cisco Firepower 2100 Series, Cisco Firepower 1000 Series, Cisco ASA 5500-X Series Firewalls, Cisco 3000 Series Industrial Security Appliances (ISA), Cisco Firepower 9000 Series, Cisco Firepower 4100 Series, Cisco Adaptive Security Virtual Appliance (ASAv), Cisco Secure Firewall 3100 Series, Cisco Secure Firewall 4200 Series

Related Products

Product CVE Evidence
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software CVE-2024-20526 Cisco OpenVuln
Cisco Secure Firewall 4200 Series CVE-2024-20526 Cisco OpenVuln
Cisco Secure Firewall 3100 Series CVE-2024-20526 Cisco OpenVuln
Cisco Firepower 9000 Series CVE-2024-20526 Cisco OpenVuln
Cisco Firepower 4100 Series CVE-2024-20526 Cisco OpenVuln
Cisco Firepower 2100 Series CVE-2024-20526 Cisco OpenVuln
Cisco Firepower 1000 Series CVE-2024-20526 Cisco OpenVuln
Cisco Adaptive Security Virtual Appliance (ASAv) CVE-2024-20526 Cisco OpenVuln
Cisco Adaptive Security Device Manager (ASDM) CVE-2024-20526 Cisco OpenVuln
Cisco Adaptive Security Appliance (ASA) Software CVE-2024-20526 Cisco OpenVuln
Cisco ASA 5500-X Series Firewalls CVE-2024-20526 Cisco OpenVuln
Cisco 3000 Series Industrial Security Appliances (ISA) CVE-2024-20526 Cisco OpenVuln