Cisco has revealed a vulnerability within two of its software that allows hackers to cause a denial of service (DoS), which is being actively exploited.
Specifically, the vulnerability was found in the Session Initiation Protocol (SIP) inspection engine of Cisco Adaptive Security Appliance (ASA) software and Cisco Firepower Threat Defense (FTD) software.
An external party could cause an affected device to reload or trigger "high CPU' resulting in a DoS.
"The vulnerability is due to improper handling of SIP traffic. An attacker could exploit this vulnerability by sending SIP requests designed to specifically trigger this issue at a high rate across an affected device," Cisco stated on its security advisories and alerts page.
Cisco did not have any updates available to fix the problem at the time of writing.
"Software updates that address this vulnerability are not yet available. There are no workarounds that address this vulnerability. Mitigation options that address this vulnerability are available."
The vulnerability affects Cisco ASA software release 9.4 and later and Cisco FTD Software Release 6.0 and later if SIP inspection is enabled and the software is running on specific products.
Those products include 3000 Series Industrial Security Appliance (ISA), ASA 5500-X Series Next-Generation Firewalls, ASA Services Module for Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers and Adaptive Security Virtual Appliance (ASAv).
The vulnerability is also found on Firepower 2100 and 4100 Series Security Appliance, Firepower 9300 ASA Security Module and FTD Virtual (FTDv).
SIP inspection is enabled by default in both Cisco ASA Software and Cisco FTD Software.
More detailed information on workarounds and how the vulnerabilities work can be found on Cisco's security advisories and alerts page.