CVE-2019-17190: A Local Privilege Escalation issue was discovered in Avast Secure Browser 76.0.1659.101. The vulnerability is due to an insecure ACL set by the AvastB...

Description

A Local Privilege Escalation issue was discovered in Avast Secure Browser 76.0.1659.101. The vulnerability is due to an insecure ACL set by the AvastBrowserUpdate.exe (which is running as NT AUTHORITY\SYSTEM) when AvastSecureBrowser.exe checks for new updates. When the update check is triggered, the elevated process cleans the ACL of the Update.ini file in %PROGRAMDATA%\Avast Software\Browser\Update\ and sets all privileges to group Everyone. Because any low-privileged user can create, delete, or modify the Update.ini file stored in this location, an attacker with low privileges can create a hard link named Update.ini in this folder, and make it point to a file writable by NT AUTHORITY\SYSTEM. Once AvastBrowserUpdate.exe is triggered by the update check functionality, the DACL is set to a misconfigured value on the crafted Update.ini and, consequently, to the target file that was previously not writable by the low-privileged attacker.

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.52%

40.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-863

Affected Software

Vendor	Product	Versions
Avast	Secure Browser	76.0.1659.101

References

http://packetstormsecurity.com/files/156844/Avast-Secure-Browser-76.0.1659.101-Local-Privilege-Escalation.htmlThird Party Advisory, VDB Entry
http://seclists.org/fulldisclosure/2020/Mar/25Mailing List, Third Party Advisory
https://www.avast.com/bug-bounty-credits/en/a-tribute-to-our-security-research-communityVendor Advisory
http://packetstormsecurity.com/files/156844/Avast-Secure-Browser-76.0.1659.101-Local-Privilege-Escalation.htmlThird Party Advisory, VDB Entry
http://seclists.org/fulldisclosure/2020/Mar/25Mailing List, Third Party Advisory
https://www.avast.com/bug-bounty-credits/en/a-tribute-to-our-security-research-communityVendor Advisory

Timeline

Published: Jan 27, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2019-17190?

A Local Privilege Escalation issue was discovered in Avast Secure Browser 76.0.1659.101. The vulnerability is due to an insecure ACL set by the AvastBrowserUpdate.exe (which is running as NT AUTHORITY\SYSTEM) when AvastSecureBrowser.exe checks for new updates. When the update check is triggered, the elevated process cleans the ACL of the Update.ini file in %PROGRAMDATA%\Avast Software\Browser\Update\ and sets all privileges to group Everyone. Because any low-privileged user can create, delete, or modify the Update.ini file stored in this location, an attacker with low privileges can create a hard link named Update.ini in this folder, and make it point to a file writable by NT AUTHORITY\SYSTEM. Once AvastBrowserUpdate.exe is triggered by the update check functionality, the DACL is set to a misconfigured value on the crafted Update.ini and, consequently, to the target file that was previously not writable by the low-privileged attacker.

How severe is CVE-2019-17190?

CVE-2019-17190 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.52% probability of exploitation in the next 30 days.

How do I fix CVE-2019-17190?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.