Scfilter Cid87d25e32ac0d4ef0b1e0502c6b7dfb77 Patched May 2026

Pre-Patch (Vulnerable Logic):

// Vulnerable logic: If Length is 0, subtraction wraps around
if (InputBufferLength < HEADER_SIZE) return STATUS_BUFFER_TOO_SMALL;
// Issue: Logic error allows bypass under specific race conditions or crafted lengths
ULONG DataSize = InputBufferLength - HEADER_SIZE;
RtlCopyMemory(Destination, Source, DataSize);

Post-Patch (CID 87d25e32ac0d4ef0b1e0502c6b7dfb77):

// Patched logic: Strict validation
if (InputBufferLength < HEADER_SIZE || InputBufferLength > MAX_IOCTL_SIZE) 
    return STATUS_INVALID_PARAMETER;
// Additional check for integer overflow
if (InputBufferLength - HEADER_SIZE > RemainingPoolSize) 
return STATUS_BUFFER_OVERFLOW;
 scfilter cid87d25e32ac0d4ef0b1e0502c6b7dfb77 patched
// Secure copy
RtlSecureCopyMemory(Destination, Source, DataSize);

1. The Vulnerability The unpatched version of SCFilter contained a flaw in how it processed certain I/O control (IOCTL) messages. Specifically, the driver failed to properly validate the size of the input buffer passed by user-mode applications.

2. The Patch (CID 87d25e32ac0d4ef0b1e0502c6b7dfb77) The patch introduces rigorous boundary checks before the driver processes any payload data. Pre-Patch (Vulnerable Logic): // Vulnerable logic: If Length

Objective: Understand the role and behavior of a specifically identified filter within a system, acknowledging that it has undergone modifications.

Possible Aspects to Investigate: