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CVE-2020-15480

Description

The DirectIo32.sys and DirectIo64.sys kernel drivers distributed with the BurnInTest, PerformanceTest and OSForensics applications by PassMark Software expose an IOCTL functionality that allows low-privilege users to read and write arbitrary Model Specific Registers (MSRs). This could lead to arbitrary Ring-0 code execution and escalation of privileges.

Impact

High - Arbitrary Ring-0 code execution

Exploitability

Medium/Low - Driver must be loaded prior to the exploitation in order to be utilized by low-privilege users, otherwise the attacker will require admin rights for the driver installation.

Technical Details

The driver offers a rdmsr and wrmsr functionality exposed via IOCTL that allows an unprivileged usermode program to read and write arbitrary CPU MSR. This can be leveraged by the attackers to patch the critical MSRs like IA32_LSTAR (0xC0000082) or IA32_SYSENTER_EIP (0x00000176) in order to achieve kernel code execution. Although many kernel exploit mitigation techniques exist, this is a viable exploit even on the newest Windows 10 systems (as of August 2020). The vulnerable IOCTLs:

IOCTL_READ_MSR  = 0x80112060
IOCTL_WRITE_MSR = 0x80112088

Resolution

The fix is distributed as a part of the August 2020 updates of the vendor's products.

Reporter

This vulnerability was discovered and reported by Michal Poslušný.

Disclosure Timeline

  • 23 June 2020 - Issue reported to vendor
  • 23 June 2020 - Vendor responded and confirmed the issues
  • 15 July 2020 - Vendor shared a test version of the driver with the issues addressed
  • 24 July 2020 - Vendor released a final version of the driver
  • 6 August 2020 - Integration of the fixed version of the driver into the vendor's products started

References