Security Advisories

FSC-2015-3: Local privilege escalation


An Access Control List (ACL) bypass in the F-Secure Gatekeeper driver allows local privilege escalation through kernel memory corruption.

Affected Products

  • Risk Level (Low/Medium/High/Cricital) High


  • F-Secure Gatekeeper driver - FSGK.SYS

Corporate products:

  • F-Secure Client Security
  • F-Secure Client Security Premium
  • F-Secure Anti-Virus for Workstations
  • F-Secure Server Security
  • F-Secure Server Security Premium
  • F-Secure Email and Server Security
  • F-Secure Email and Server Security Premium 
  • F-Secure Protection Service for Business (PSB) Workstation Security
  • F-Secure Protection Service for Business (PSB) Server Security
  • F-Secure Protection Service for Business (PSB) Email and Server Security 

Consumer Products:

  • F-Secure Safe Anywhere PC 
  • F-Secure Internet Security
  • F-Secure Anti-Virus 
  • F-Secure Ultralight Anti-Virus Beta


  • Risk Level (Low/Medium/High/Cricital) High
  • Windows 

More Information

It was discovered that it is possible to bypass the Access Control List (ACL) for the F-Secure Gatekeeper device driver, even when access rights is given only to an Administrator or SYSTEM account. This is caused by the missing flag of FILE_DEVICE_SECURE_OPEN when creating an object. A successful bypass of the ACL will allow an attacker to manipulate the kernel buffer allocation, resulting in a memory corruption. Successful exploitation will result in a local privilege escalation of a normal user account to an administrator or system account.

Fix Available

Component Version Remark
fsgk.sys Fix is available in the automatic update channel for all affected products. No user action is needed if automatic updates is enabled.


F-Secure Corporation would like to thank Ilja van Sprundel from IOActive and Thierry Decroix for bringing this issue to our attention.

Date Issued: 2015-09-01