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Improper Link Resolution Before File Access ('Link Following')


Severity High
Score 7.8/10


A vulnerability has been discovered in cloudflared's installer in versions prior to 2023.3.1 for Windows 32-bits devices that allows a local attacker with no administrative permissions to escalate their privileges on the affected device. This vulnerability exists because the MSI installer used by cloudflared relied on a world-writable directory. An attacker with local access to the device (without Administrator rights) can use symbolic links to trick the MSI installer into deleting files in locations that the attacker would otherwise have no access to. By creating a symlink from the world-writable directory to the target file, the attacker can manipulate the MSI installer's repair functionality to delete the target file during the repair process. The exploitation of this vulnerability could allow an attacker to delete important system files or replace them with malicious files, potentially leading to the affected device being compromised. The cloudflared client itself is not affected by this vulnerability, only the installer for 32-bit Windows devices.

  • LOW
  • HIGH
  • NONE
  • LOW
  • HIGH
  • HIGH

CWE-59 - Improper Link Resolution Before File Access

'Improper link resolution before file access' occurs when software accesses a file resource but fails to verify that the file isn't a link or shortcut to another file. An attacker can potentially gain access to arbitrary files and from there the impact can vary, depending on the application, from sensitive data exposure to remote code execution.


Advisory Timeline

  • Published