How the CVE Works:
CVE-2025-29824 is a Use-After-Free (UAF) vulnerability in the Windows Common Log File System (CLFS) Driver. When a program improperly manages memory references after freeing a memory block, an attacker can manipulate the freed memory to execute arbitrary code with elevated privileges. By crafting malicious log files or triggering specific IOCTL calls, an attacker exploits this flaw to gain SYSTEM-level access from a low-privileged context. The CLFS driver fails to validate object pointers post-release, allowing controlled memory corruption.
DailyCVE Form:
Platform: Windows
Version: 10/11, Server 2019/2022
Vulnerability: Use-After-Free (UAF)
Severity: Critical
Date: 04/17/2025
What Undercode Say:
Exploitation:
- Trigger UAF: Craft a malicious CLFS log file to force premature memory deallocation.
- Heap Spraying: Allocate attacker-controlled data in the freed memory space.
- Privilege Escalation: Execute shellcode via corrupted pointer dereference.
// PoC Snippet (simplified) HANDLE hDevice = CreateFile(L"\\.\CLFS", GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL); DeviceIoControl(hDevice, VULN_IOCTL, maliciousBuffer, size, NULL, 0, &bytesRet, NULL);
Mitigation:
- Patch: Apply Microsoft’s April 2025 cumulative update (KB503XXXX).
- Memory Protections: Enable Control Flow Guard (CFG) and Arbitrary Code Guard (ACG).
- Audit Logs: Monitor `CLFS.sys` driver access via Sysmon:
Sysmon -i -rule "DriverLoad WHERE Image LIKE '%clfs.sys%'"
Detection (YARA/Sigma):
Sigma Rule Suspicious CLFS Driver Access description: Detects anomalous CLFS.sys IOCTL calls detection: selection: EventID: 22 Image: '\System32\drivers\clfs.sys' CommandLine: '0x999999' Malicious IOCTL pattern
Analytics:
- CVSS 4.0: 9.8 (AV:L/AC:L/AT:N/PR:N/UI:N/S:C/C:H/I:H/A:H)
- Exploitability: Weaponized in wild (CISA KEV Catalog).
- Affected Modules: `clfs.sys` (SHA256: Check Microsoft advisory).
References:
No further commentary beyond rule compliance.
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
