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A Vulnerability in TeamViewer Cloud Allow for Offline Password Cracking

MS-ISAC ADVISORY NUMBER:

2020-106

DATE(S) ISSUED:

08/05/2020

OVERVIEW:

A vulnerability has been discovered in TeamViewer, which could allow for offline password cracking. TeamViewer is a program used for remote control, desktop sharing, online meetings, web conferencing, and file transfer between systems. Successful exploitation of this vulnerability could allow an attacker to launch TeamViewer with arbitrary parameters. The program could be forced to relay an NTLM authentication request to the attacker’s system allowing for offline rainbow table attacks and brute force cracking attempts. These attacks could lead to further exploitation due to stolen credentials from successful exploitation of this vulnerability.

THREAT INTELLIGENCE:

There are currently no reports of this vulnerability being exploited in the wild.

SYSTEMS AFFECTED:

  • TeamViewer versions prior to 15.8.3

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: MEDIUM
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: MEDIUM
Home Users:
LOW

TECHNICAL SUMMARY:

A vulnerability has been discovered in TeamViewer, which could allow for offline password cracking. Specifically, this vulnerability is due to the program not properly quoting its custom URI handlers. This vulnerability can be exploited when the system visits a maliciously crafted website.

Successful exploitation of this vulnerability could allow an attacker to launch TeamViewer with arbitrary parameters. The program could be forced to relay an NTLM authentication request to the attacker’s system allowing for offline rainbow table attacks and brute force cracking attempts. These attacks could lead to further exploitation due to stolen credentials from successful exploitation of this vulnerability.

RECOMMENDATIONS:

We recommend the following actions be taken:

  • Apply appropriate patches from TeamViewer to the vulnerable systems after appropriate testing.
  • Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
  • Inform and educate users regarding threats posed by hypertext links contained in emails or attachments, especially from un-trusted sources.

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