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Cisco Adaptive Security Appliance Software and Firewall Services Module Software Secure Shell Denial of Service Vulnerability

Cisco-SA-20130412-CVE-2013-1193 · Medium · Published · Updated

A vulnerability in the implementation of the Secure Shell (SSH) function could allow an unauthenticated, remote attacker to deny SSH management access to legitimate users. The vulnerability is due to improper implementation of the logic to terminate SSH sessions. An attacker could exploit this vulnerability by starting an SSH session to the affected system. This vulnerability affects both SSHv1 and v2. An exploit could allow the attacker to deny SSH management access to legitimate users. The attacker can deny the access for 60 seconds, and then the affected system will release the resource and users will be able to use the SSH service again. However, repeated exploitation may lead to a denial of service condition. Cisco has confirmed the vulnerability in a security notice and software updates are available. An attacker can only deny access to a targeted system for 60 seconds, which then the affected system will release the resource to allow legitimate users SSH access again. However, repeated exploitation could lead to a sustained DoS condition. Customers are advised to review the bug report in the vendor announcements section for a current list of affected versions. Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.

Cisco advisory · CSAF JSON

Workarounds

Administrators are advised to apply the appropriate updates.

Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.

Administrators are advised to allow only privileged users to access administration or management systems.

It is critical to prevent unauthorized direct communication to network devices. Restrict network traffic destined for the network infrastructure to protect against reconnaissance and DoS attacks. For configuration details, consult Protecting Your Core: Infrastructure Protection Access Control Lists["http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801a1a55.shtml"].

Administrators may consider using the HTTPS management interface instead of the SSH management access.

Administrators are advised to monitor affected systems.

CVEsCVE-2013-1193
Cisco Bug IDsCSCue63881, CSCue78671, CSCuf51892, CSCug26937
CVSS ScoreBase 5.0
Base 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P/E:F/RL:OF/RC:C
Base 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P/E:F/RL:W/RC:C
Product Names From Source
Cisco Firewall Services Module (FWSM), Cisco Adaptive Security Appliance (ASA) Software 8.4.1, Cisco Adaptive Security Appliance (ASA) Software 8.4.2, Cisco Adaptive Security Appliance (ASA) Software 8.4.1.3, Cisco Adaptive Security Appliance (ASA) Software 8.4.1.11, Cisco Adaptive Security Appliance (ASA) Software 8.4.2.8, Cisco Adaptive Security Appliance (ASA) Software 8.4.3, Cisco Adaptive Security Appliance (ASA) Software 8.4.3.8, Cisco Adaptive Security Appliance (ASA) Software 8.4.3.9, Cisco Adaptive Security Appliance (ASA) Software 8.4.4, Cisco Adaptive Security Appliance (ASA) Software 8.4.4.1, Cisco Adaptive Security Appliance (ASA) Software 8.4.4.3, Cisco Adaptive Security Appliance (ASA) Software 8.4.4.5, Cisco Adaptive Security Appliance (ASA) Software 8.4.4.9, Cisco Adaptive Security Appliance (ASA) Software 8.4.5, Cisco Adaptive Security Appliance (ASA) Software 8.4.5.6, Cisco Adaptive Security Appliance (ASA) Software 8.4.6, Cisco Adaptive Security Appliance (ASA) Software

Related Products

Product CVE Evidence
Cisco Firewall Services Module (FWSM) CVE-2013-1193 Cisco OpenVuln
Cisco Adaptive Security Appliance (ASA) Software CVE-2013-1193 Cisco OpenVuln