Windows Hard Link in Avast Secure Browser - CVE-2019-17190

Vulnerability details

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to software sets insecure permission to C:ProgramDataAVAST SOFTWAREBrowserUpdateUpdate.ini file. This file is used during application update procedure and its permissions are replaced by the "AvastBrowserUpdate.exe" program, which runs under "NT AUTHORITYSYSTEM" account. A local user can create a hard link from the Update.ini file to any file on the system and replace permissions of arbitrary file.

Successful exploitation of the vulnerability may allow an attacker to escalate privileges on the system.

Affected software

How to mitigate CVE-2019-17190

Links to Public Exploits and PoC-codes

• Exploit #2227 - Vulnerability in Avast Secure Browser enables escalation of privileges on Windows (March 21, 2020)

External References

• http://seclists.org/fulldisclosure/2020/Mar/25
• https://www.avast.com/bug-bounty-credits/en/a-tribute-to-our-security-research-community
• https://sidechannel.tempestsi.com/vulnerability-in-avast-secure-browser-enables-escalation-of-privileges-on-windows-eb770d196c45

Related Security Bulletins

• Privilege escalation in Avast Secure Browser