Cisco AnyConnect Secure: authentication bypass flaw under attack

What is affected

Cisco AnyConnect Secure is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

Cisco AnyConnect Secure Mobility Client for Windows interprocess communication (IPC) channel allows for insufficient validation of resources that are loaded by the application at run time. An attacker with valid credentials on Windows could execute code on the affected machine with SYSTEM privileges.

What an attacker can do

This is a authentication bypass flaw. It lets an attacker get in without a valid username and password and act as a legitimate user, often as an administrator.

How it is reached

Needs access to the device or a file opened on it

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

CISA records this vulnerability as known to be used in ransomware campaigns: attackers use it to get in, then encrypt files and demand payment.

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer Cisco AnyConnect Secure at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply updates per vendor instructions.

Vendor advisories and fixes

• tools.cisco.comtools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-dll-F26W

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on October 24, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by November 14, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 10% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 96% of all scored vulnerabilities.

Its CVSS severity score is 7.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client for Windows could allow an authenticated, local attacker to perform a DLL hijacking attack. To exploit this vulnerability, the attacker would need to have valid credentials on the Windows system. The vulnerability is due to insufficient validation of resources that are loaded by the application at run time. An attacker could exploit this vulnerability by sending a crafted IPC message to the AnyConnect process. A successful exploit could allow the attacker to execute arbitrary code on the affected machine with SYSTEM privileges. To exploit this vulnerability, the attacker would need to have valid credentials on the Windows system.