CVE-2021-32022 Low Privilege Deleteįollowing on from the large RPC message as described above for CVE-2021-32021, the ReadFileMessage function was found to delete the RPC message file once the contents had been consumed. The net result of this was no more detection of viruses or malware since the service was no longer operational. This will cause a denial of service within the Cylance service. If the RPC message file increases in size between the first and second call to ReadFileMessage, the heap is overflowed when the memcpy function is called. Unfortunately, the ReadFileMessage function will a second time determine the file size using the GetFileSize API instead of using the fileSize variable that was already determined on the previous call. The second call to ReadFileMessage then proceeds to pass in the block of allocated memory for reading. This is used to allocate the memory to store the file contents using malloc. On its return, the variable is populated with the current fileSize. The first call to ReadFileMessage passes a pointer to the fileSize variable. The bug it a type of TOCTOU (Time-Of-Check Time-Of-Use) class where the size of the allocated heap memory is not sufficient to hold the entire contents of the file. If the message starts with the string it is assumed the remaining part of the RPC message is a path to a local file on disk. When Cylance is required to send a larger RPC message, a special token is sent over the RPC mechanism to indicate that the RPC message should be read from a local file on disk instead. The RPC mechanism limits the request size to 64k, most likely due to certain RPC limits present within older generations of Windows. NET but there is a native DLL that handles the dispatch of RPC calls to different components called CefServer.dll, and in here lies the problem.
Cylance antivirus cef format software#
The software is predominantly written in. ALPC by its very nature is designed for local inter-process communication only, therefore the vulnerability is limited to local attack only. CVE-2021-32021 Denial of ServiceĬylance uses an intricate message broker system where various components of the software communicate over RPC using the ALPC mechanism. Further information on the advisory can be found here. It is recommended that the software is either upgraded to the latest 158x stream or version 1578 at the time of writing. CVE-2021-32023 – Elevation of privilege in message broker.Ī heap overflow resulting in a denial of service, low privilege arbitrary file delete and an elevation of privilege from limited service accounts to SYSTEM.CVE-2021-32022 – Low privileged delete using CEF RPC server.CVE-2021-32021 – Denial of service in message broker.
Cylance antivirus cef format windows#
For more information, see: Necessity of deleting Quarantined files in Cylance Smart Antivirus.Blackberry Cylance for Windows is affected by three vulnerabilities. Note: Quarantined threats are removed from the device automatically.
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