Windows UAC Bypass Vulnerability

A bypass vulnerability has been identified in the User Account Control (UAC) feature on Windows 10 devices. The UAC prompt appears when users attempt to execute processes that require privilege escalation.

Threat ID:: CC-2792
Category:
Threat Severity:: Medium
Threat Vector:: Vulnerability
Published:: 15 November 2018 12:00 AM

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Summary

Affected platforms

The following platforms are known to be affected:

Windows 10

Microsoft Windows - Version 10

Threat details

However, certain processes are exempt and will automatically escalate after undergoing additional security checks.

Initially, a spoofed directory can be created by using the CreateDirectory API, prepending a “\\?\” to the directory name and appending a space. A properly signed, automatically escalating executable can be copied from the genuine directory without receiving a UAC prompt. When the executable is run, Appinfo.dll passes it to the GetLongPathNameW API which results in the spoofed directory path being converted back to the genuine directory path. The trusted directory checks are then performed against the genuine directory, rather than the spoofed directory, resulting in all other checks being allowed to pass. Appinfo.dll completes the process by automatically escalating the privileges of the executable copy.

An attacker can exploit this vulnerability to deliver malicious files through spoofed directories.

For further information:

UAC Bypass Proof of Concept

Remediation steps

Type	Step
	At the time of publication, there is no indication of when an update that addresses this vulnerability will be released. To prevent and detect an infection in the meantime, ensure that: A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails. All operating systems, anti-virus and other security products are kept up-to-date. All day-to-day computer activities such as email and internet are performed using non-administrative accounts. Strong password policies are in place. Network, proxy and firewall logs should be monitored for suspicious activity. User accounts accessed from affected devices should be reset on a clean computer. Your organisation adopts a holistic all-round approach to Cyber Security as advocated by the 10 Steps to Cyber Security.

Type

Step

At the time of publication, there is no indication of when an update that addresses this vulnerability will be released.

To prevent and detect an infection in the meantime, ensure that:

A robust program of education and awareness training is delivered to users to ensure they don’t open attachments or follow links within unsolicited emails.
All operating systems, anti-virus and other security products are kept up-to-date.
All day-to-day computer activities such as email and internet are performed using non-administrative accounts.
Strong password policies are in place.
Network, proxy and firewall logs should be monitored for suspicious activity.
User accounts accessed from affected devices should be reset on a clean computer.
Your organisation adopts a holistic all-round approach to Cyber Security as advocated by the 10 Steps to Cyber Security.

Last edited: 17 February 2020 12:59 pm