Security Experts:

Microsoft Makes Third Attempt at Fixing Old Stuxnet Flaw

One of the patches released by Microsoft as part of its June 2017 security updates represents the company’s third attempt at patching an old vulnerability exploited by the notorious Stuxnet worm in 2010.

The initial vulnerability, tracked as CVE-2010-2568, allows a remote attacker to execute arbitrary code on a system using specially crafted shortcut files with the LNK or PIF extension.

CVE-2010-2568 was one of the four zero-day vulnerabilities exploited in the 2010 Stuxnet attacks targeting Iran’s nuclear program. Despite being patched by Microsoft in August 2010, it has remained one of the most exploited vulnerabilities.

In 2015, researchers discovered that Microsoft’s initial fix could be bypassed and the tech giant released another patch. The flaw, tracked as CVE-2015-0096, was treated by Microsoft as a completely new issue.

According to an advisory published on Thursday by the CERT Coordination Center at Carnegie Mellon University, someone discovered another method for bypassing Microsoft’s patches for this weakness. No information has been provided as to who discovered the new vulnerability.

“The fix for CVE-2010-2568 and the subsequent fix for CVE-2015-0096 are both insufficient in that they not take into account LNK files that use the SpecialFolderDataBlock or KnownFolderDataBlock attributes to specify the location of a folder. Such files are able to bypass the whitelisting first implemented in the fix for CVE-2010-2568,” CERT/CC said in its advisory.

“By convincing a user to display a specially-crafted shortcut file, an attacker may be able to execute arbitrary code with the privileges of the user. Depending on the operating system and AutoRun/AutoPlay configuration, this can happen automatically by connecting a USB device,” the advisory explained.

CERT/CC pointed out that Microsoft patched the new vulnerability, tracked as CVE-2017-8464, with its June security updates. Microsoft informed customers at the time that this flaw had been exploited in the wild. Exploits for the security hole are now publicly available, including a Metasploit module made by Securify's Yorick Koster.

The organization pointed out that in addition to applying Microsoft’s patches, users can prevent potential attacks by blocking outgoing connections on TCP and UDP ports 139 and 445. This prevents machines from accessing a remote SMB server, which is typically needed to exploit the vulnerability.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.