Cisco Adaptive Security Appliance (ASA) Software contains a vulnerability that could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.
The vulnerability is due to the incorrect management of remote SSH sessions when two or more sessions are active to the ASA console. An authenticated, remote attacker could exploit this vulnerability by logging multiple SSH sessions to the targeted device. If successful, the attacker could cause the device to crash, resulting in a DoS condition.
Proof-of-concept code that exploits the vulnerability is publicly available.
Cisco has confirmed the vulnerability in a security notice and released software updates.
Indicators of Compromise
Cisco ASA Software versions 8.4(1) and prior are vulnerable.
The vulnerability is due to the incorrect management of remote SSH sessions when two or more sessions are active to the ASA console.
An authenticated, remote attacker could exploit this vulnerability by logging multiple SSH sessions to the targeted device, which could cause one of the sessions to time out. If successful, an attacker could cause the device to crash, resulting in a DoS condition.
To exploit this vulnerability, an attacker must be able to authenticate to a targeted device to activate multiple SSH sessions, likely requiring the attacker to access trusted, internal networks. This access requirement limits the likelihood of a successful exploit.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators are advised to monitor affected systems.
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at email@example.com.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.