CVE-2021-27241: avast premium_security Link Following

Vulnerability summary

CVE-2021-27241 is a medium (CVSS 6.1) Link Following vulnerability in avast premium_security. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 18.1% of scored vulnerabilities.

Timeline

1. 29-03-2021
   PublishedVulnerability first disclosed.
2. 03-08-2024
   Last modifiedVulnerability information updated.

Description

This vulnerability allows local attackers to delete arbitrary directories on affected installations of Avast Premium Security 20.8.2429 (Build 20.8.5653.561). An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the AvastSvc.exe module. By creating a directory junction, an attacker can abuse the service to delete a directory. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-12082.

• CWE-59Improper Link Resolution Before File Access ('Link Following')The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.