✅ Report Title: Windows Common Log File System Driver Vulnerability: CVE-2025–32713

✅ Executive Summary:

- The S2W Threat Intelligence Center, TALON have identified a Local Privilege Escalation (LPE) vulnerability in the Windows Common Log File System (CLFS) driver, caused by a pool-based memory overflow.

- The vulnerability is triggered when reading a log block using a context mode other than ClfsContextForward on volumes with logical sector sizes greater than 512 bytes.

- This condition allows user-controlled data to be written into unintended memory regions, potentially leading to privilege escalation.

- The vulnerability remains exploitable even with CLFS HMAC mitigation enabled.

📌 What is the Root Cause of the Vulnerability?

- When a user reads a specific log record from a CLFS container stored on disk, the CLFS driver invokes the CClfsLogFcbPhysical::ReadLogBlock function through several stages, regardless of whether the user-mode log marshalling area is enabled. This function subsequently calls CcCopyRead to retrieve the requested log block.

- If the CLFS container resides on a volume with a logical sector size larger than 512 bytes, and the read operation uses a context mode other than ClfsContextForward, a pool overflow can occur. This flaw can be exploited by a local user to elevate privileges.

📌 How Can This Vulnerability Be Exploited?

- Conditions: The target system must contain a volume with a logical sector size larger than 512 bytes that grants read and write access to all users.

- The attacker gains code execution capabilities at Medium Integrity Level through exploitation of system or application vulnerabilities or through social engineering.

- Using known KASLR (Kernel Address Space Layout Randomization) bypass techniques, the attacker deduces the kernel's memory layout.

- The attacker creates a CLFS log container on the identified volume and embeds carefully crafted fake kernel objects based on the inferred layout.

- By initiating a read request from this container using a context mode other than ClfsContextForward, the vulnerability is triggered, causing a pool overflow that writes the fake kernel objects into adjacent memory regions.

- When kernel-mode functions access the corrupted memory, the attacker can leverage this to gain elevated (administrator-level) privileges.