Microsoft MsMpEng – Multiple Crashes While Scanning Malformed Files
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1261 A detailed introduction to MsMpEng can be found in issue #1252 , so I will skip the background story here. Through fuzzing, we have discovered a number of ways to crash the service (and specifically code in the mpengine.dll module), by feeding it with malformed input testcases to scan. A summary of our findings is shown in the table below: +==============+===================================+==========================+=============+====================================================+=============================================+ | Name | Type | Requirements | Access Type | Observed symbol | Comments | +==============+===================================+==========================+=============+====================================================+=============================================+ | corruption_1 | Heap buffer overflow | PageHeap for MpMsEng.exe | - | free() called by NET_thread_ctx_t__FreeState_void_ | One-byte overflow. | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | corruption_2 | Heap corruption | PageHeap for MpMsEng.exe | - | free() called by CRsaPublicKey__Decrypt_uchar | May crash in other ways, e.g. invalid read. | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | corruption_3 | Unspecified memory corruption (?) | - | - | netvm_parse_routine_netinvoke_handle_t | Different crashes with/out PageHeap. | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | null_1 | NULL Pointer Dereference | - | READ | nUFSP_pdf__handleXFA_PDF_Value | | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | null_2 | NULL Pointer Dereference | - | READ | nUFSP_pdf__expandObjectStreams_void | | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | null_3 | NULL Pointer Dereference | - | READ | NET_context_unsigned | | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | null_4 | NULL Pointer Dereference | - | READ | nUFSP_pdf__expandObjectStreams_void_ | Similar to null_2, may be the same bug. | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | div_by_zero | Division by zero | - | - | x86_code_cost__get_cost_int | | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ | recursion | Deep/infinite recursion | - | - | __EH_prolog3_catch_GS | | +--------------+-----------------------------------+--------------------------+-------------+----------------------------------------------------+---------------------------------------------+ The "corruption_1-3" issues are the most important ones, as they represent memory corruption problems and could potentially lead to execution of arbitrary code. On the other hand, "null_1-4", "div_by_zero" and "recursion" are low severity bugs that can only be used to bring the service process down. We have verified that all listed crashes occur on Windows 7 as soon as an offending sample is saved to disk and discovered by MsMpEng. For "corruption_1-2", the PageHeap mechanism must be enabled for the MsMpEng.exe program in order to reliably observe the unhandled exception. Attached is a ZIP archive (password: "mpengbugs") with up to 3 testcases for each of the 9 unique crashes. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/42081.zip |