A security researcher found a severe TeamViewer vulnerability affecting Windows versions of the application 8 through 15, allowing attackers to steal system credentials.
TeamViewer is a powerful tool for remote administration, but that also means it’s already a prime target for hackers and other bad actors. Vulnerabilities in TeamViewer are dangerous, and developers have to fix them as quickly as possible.
TeamViewer recently issued a patch covering this severe vulnerability (CVE 2020-13699) as the problem affected a vast array of versions, including many still in operation. When exploited, the vulnerability lets an attacker steal the system password, making it trivial to further compromise the operating system.
“TeamViewer Desktop for Windows before 15.8.3 does not properly quote its custom URI handlers. A malicious website could launch TeamViewer with arbitrary parameters, as demonstrated by a teamviewer10: –play URL,” says the CVE advisory. “An attacker could force a victim to send an NTLM authentication request and either relay the request or capture the hash for offline password cracking.”
Bad actors could set up a phishing site with a malicious iframe, which would launch the TeamViewer client when the victim opened the website. What makes the vulnerability especially dangerous is that it would happen with little input from the user.
The developers said the vulnerability doesn’t seem to be actively used in the wild. Now that the exploit’s details are public, though, hackers will most likely make use of it. Since TeamViewer is a popular application, it will take a long time for people to upgrade their clients, allowing attackers to exploit this security issue for quite a while.
The only solution is to update TeamViewer to the latest version as soon as possible.