Lenovo Patches Privilege Escalation Flaws in System Update

Lenovo has released a new version of its System Update software to address a couple of privilege escalation vulnerabilities discovered by an IOActive researcher.

Lenovo System Update, previously known as ThinkVantage System Update, is a piece of software designed to help users quickly obtain driver, BIOS and application updates for Lenovo and Think systems.

The first vulnerability identified by IOActive researcher Sofiane Talmat can be exploited by a local unprivileged attacker to gain administrator privileges on the targeted system (CVE-2015-8109). The flaw, rated “critical” by the company, is related to a temporary administrator account created when System Update is executed.

According to an advisory from IOActive, since System Update can be run even by unprivileged users, the System Update service SUService.exe, which has system privileges, creates a temporary admin account and uses it to launch the update tool’s graphical interface (Tvsukernel.exe).

The problem is that while both the username and the password for the temporary admin account are randomly generated, in certain circumstances an attacker could predict the credentials and use them to gain administrator privileges on the targeted machine.

A related security bug found by Talmat allows a local unprivileged attacker to execute commands with the privileges of the Windows system user (CVE-2015-8110).

The System Update GUI application that is executed with the temporary administrator account includes links to various support pages on Lenovo’s website. When one of these links is clicked, the webpages are opened in a web browser launched using the temporary admin account, allowing an unprivileged attacker to leverage this browser session to elevate their privileges.

The vulnerabilities were reported to Lenovo on November 2 and they were patched on November 19 with the release of System Update 5.07.0019.

Lenovo has released several new versions of its System Update software this year to address a total of ten vulnerabilities, including issues reported by researchers from Trustwave, IOActive and Tencent’s Xuanwu Lab.