Microsoft Patch Tuesday, September 2019 Edition

Microsoft have issued security updates to plug some 80 security holes in various flavors of its Windows operating systems and related software. The software giant assigned a “critical” rating to almost a quarter of those vulnerabilities, meaning they could be used by malware or miscreants to hijack vulnerable systems with little or no interaction on the part of the user.

Two of the bugs quashed in this month’s patch batch involve vulnerabilities in all supported versions of Windows that have already been exploited in the wild. Both are known as “privilege escalation” flaws in that they allow an attacker to assume the all-powerful administrator status on a targeted system. Exploits for these types of weaknesses are often deployed along with other attacks that don’t require administrative rights.

September also marks the fourth time this year Microsoft has fixed critical bugs in its Remote Desktop Protocol (RDP) feature, with four critical flaws being patched in the service. These Remote Desktop flaws were discovered in a code review by Microsoft, and in order to exploit them an attacker would have to trick a user into connecting to a malicious or hacked RDP server.

Microsoft also fixed another critical vulnerability in the way Windows handles link files ending in “.lnk” that could be used to launch malware on a vulnerable system if a user were to open a removable drive or access a shared folder with a booby-trapped .lnk file on it.

Shortcut files — or those ending in the “.lnk” extension — are Windows files that link easy-to-recognize icons to specific executable programs, and are typically placed on the user’s Desktop or Start Menu. It’s perhaps worth noting that poisoned .lnk files were one of the four known exploits bundled with Stuxnet, a multi-million dollar cyber weapon that American and Israeli intelligence services used to derail Iran’s nuclear enrichment plans roughly a decade ago.

As there do not appear to be any patch-now-or-be-compromised-tomorrow flaws in the September patch rollup, it’s probably safe to say most Windows end-users would benefit from waiting a few days to apply these fixes.

Very often fixes released on Patch Tuesday have glitches that cause problems for an indeterminate number of Windows systems. When this happens, Microsoft then patches their patches to minimize the same problems for users who haven’t yet applied the updates, but it sometimes takes a few days for Redmond to iron out the kinks.