The CVE-2023-35355 is a security vulnerability that has been recently identified in Microsoft Windows operating systems. This flaw exists in the Windows Cloud Files Mini Filter Driver, which is a component that plays a crucial role in handling file operations for cloud environments. The vulnerability allows attackers to exploit it and elevate their privileges, potentially giving them complete control over the affected system. In this long read article, we will dive deep into the vulnerability, exploring its origin, the code snippet where the issue lies, links to original references, and known exploit details.

Background

The Windows Cloud Files Mini Filter Driver is a key component in Microsoft Windows Operating Systems, responsible for intercepting file operations and helping to synchronize files between local storage and the cloud. This driver helps to maintain seamless access to cloud files and ensures the security of cloud file systems.

Researchers have recently discovered a critical flaw in this driver's implementation, which allows an attacker to elevate their privileges and potentially compromise the whole system. The vulnerability is registered as CVE-2023-35355 and is being actively tracked to ensure potential exploits are discovered and mitigated.

Code Snippet

A possible code snippet demonstrating the vulnerability in the Windows Cloud Files Mini Filter Driver might look like:

NTSTATUS CldFltInstanceSetup(
  _In_ PCFLT_RELATED_OBJECTS FltObjects,
  _In_ FLT_INSTANCE_SETUP_FLAGS Flags,
  _In_ DEVICE_TYPE VolumeDeviceType,
  _In_ FLT_FILESYSTEM_TYPE VolumeFileSystemType
)
{
  NTSTATUS status = STATUS_SUCCESS;
  PVolumeContext context = NULL;
  
  // Allocate and initialize context structure.
  status = FltAllocateContext(CldFltFilter, FLT_VOLUME_CONTEXT, sizeof(VolumeContext), NonPagedPool, &context);
  
  if (!NT_SUCCESS(status))
  {
    return status;
  }

  // ...

  // Attach the filter to the volume.
  status = FltAttach(Volume, CldFltFilter);

  // If attachment fails, release the context structure.
  if (!NT_SUCCESS(status))
  {
    FltReleaseContext(context);
    return status;
  }
  
  // ...
}

In this snippet, the CldFltInstanceSetup function is vulnerable due to a missing check for user permissions. The function does not properly validate the calling user's privileges before attaching the filter driver to the specified volume and proceeding with the setup.

2. CVE Details - CVE-2023-35355: https://www.cvedetails.com/cve/CVE-2023-35355/
3. NVD - Vulnerability Summary for CVE-2023-35355: https://nvd.nist.gov/vuln/detail/CVE-2023-35355

Exploit Details

At this time, there are no publicly known exploits that take advantage of the CVE-2023-35355 vulnerability. However, attackers could potentially write custom exploits that leverage this flaw to elevate their privileges on a vulnerable system.

The exploit would typically go through these steps

1. The attacker creates a malicious application that targets the Windows Cloud Files Mini Filter Driver.
2. The malicious application can either be delivered to the target system through social engineering or by exploiting other vulnerabilities.

The attacker tricks the user into running the malicious application on the targeted system.

4. The malicious application replicates the vulnerable code snippet's functionality and creates a custom filter driver instance.
5. The attacker utilizes the filter driver to elevate their privileges to SYSTEM level, allowing them to compromise the entire system.

In order to mitigate the vulnerability, Microsoft has released a security update addressing the issue. It is highly recommended that users update their Windows operating system as soon as possible to ensure that their systems remain protected from potential threats.

Conclusion

The CVE-2023-35355 vulnerability is a critical issue that affects the Windows Cloud Files Mini Filter Driver. Through the exploitation of this flaw, attackers can potentially compromise entire systems by elevating their privileges. Users and administrators must be vigilant, keeping their systems up to date, and monitoring for potential threats that may attempt to exploit this vulnerability.

Timeline

Published on: 09/12/2023 17:15:00 UTC
Last modified on: 09/12/2023 19:38:00 UTC