The AnyConnect Secure Mobility Client allows employees to work remotely by securely connecting back to their company's network. It provides virtual private networking over SSL and additional features like identity services, network access control and Web security.
The vulnerability in the Linux and Mac OS X version of the client was discovered and reported by researchers from Dutch security firm Securify. It can be exploited to execute arbitrary files with the highest system privileges, also known as root.
The Securify researchers also reported a similar vulnerability in the Windows version of the client that allows executing malicious DLL files with the System privilege.
The Windows version flaw was also independently found by researchers from Google's Project Zero team who published proof-of-concept exploit code for it last week, after Cisco took more than 90 days to release a patch and did not ask for an extension to the public disclosure deadline.
Attackers need to first have limited access to a system before they can exploit any of the two flaws to escalate their privileges.
Version 4.1(8) of the Linux and Mac OS X client were confirmed to be vulnerable, but other versions might also be affected, Cisco said in a security alert.
All versions of the Cisco AnyConnect Secure Mobility Client for Windows before the new update were vulnerable, the company said.
Cisco customers with active contracts can obtain the latest patched versions through the company's Software Center. Additional details are provided in bug notes that are only visible to registered users.