Exploitalert - Database of Exploits

Microsoft Windows Kernel win32kbase!CoreMessagingK Memory Disclosure

CVE	Category	Price	Severity
CVE-2018-0926	CWE-200	$6000	High

Author	Risk	Exploitation Type	Date
Unknown	High	Local	2018-03-21

CPE
cpe:cpe:/o:microsoft:windows

CVSS	EPSS	EPSSP
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N	0.02192	0.50148

CVSS vector description

Metric	Value	Metric Description	Value Description
Attack vector	Local	AV	The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity	Low	AC	The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required	None	PR	The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction	None	UI	The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope	Unchanged	S	An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality	High	C	There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity	None	I	There is no impact on the integrity of the system; the attacker does not gain the ability to modify any files or information on the target system.
Availability	None	A	There is no impact on the availability of the system; the attacker does not have the ability to disrupt access to or use of the system.

https://cxsecurity.com/ascii/WLB-2018030176

Microsoft Windows Kernel win32kbase!CoreMessagingK Memory Disclosure

Windows Kernel 64-bit pool memory disclosure in the win32kbase!CoreMessagingK interface CVE-2018-0926 We have discovered that the the win32kbase.sys driver sends an ALPC message with portions of uninitialized memory from the paged pool on Windows 10 64-bit (1709). We observed this behavior very early in the system boot process. The message is 0xd0 (208) bytes long, 4 of which are uninitialized. The layout of the memory area is as follows: --- cut --- 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000020: 00 00 00 00 ff ff ff ff 00 00 00 00 00 00 00 00 ................ 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 000000a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 000000b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 000000c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ --- cut --- Where 00 denote bytes which are properly initialized, while ff indicate uninitialized values. This buffer can be then read back into user-mode with e.g. the nt!NtAlpcSendWaitReceivePort syscall, as observed during system runtime on our test machine: --- cut --- kd> k # Child-SP RetAddr Call Site 00 ffffea89`95743a28 fffff801`5f6ef358 nt!memcpy+0x3 01 ffffea89`95743a30 fffff801`5f6eedb9 nt!AlpcpReceiveMessage+0x408 02 ffffea89`95743b10 fffff801`5f388553 nt!NtAlpcSendWaitReceivePort+0xf9 03 ffffea89`95743bd0 00007ffd`8f8d0f54 nt!KiSystemServiceCopyEnd+0x13 04 00000050`5e67f428 00007ffd`898fda8f ntdll!NtAlpcSendWaitReceivePort+0x14 05 00000050`5e67f430 00007ffd`89902fd7 coremessaging!AlpcConnection::Callback_ProcessIncoming+0x9f 06 00000050`5e67f4f0 00007ffd`898cf606 coremessaging!Microsoft::CoreUI::Registrar::AlpcServerAdapter$R::Delegate0+0x47 07 00000050`5e67f540 00007ffd`898d8f53 coremessaging!Microsoft::CoreUI::Dispatch::WaitController$R::Delegate1+0x86 08 00000050`5e67f590 00007ffd`898d8b47 coremessaging!Microsoft::CoreUI::Dispatch::WaitController::Callback_DoGeneralWait+0x283 09 00000050`5e67f6d0 00007ffd`898d5916 coremessaging!Microsoft::CoreUI::Dispatch::WaitController::Callback_OnDispatch+0x457 0a 00000050`5e67f790 00007ffd`898d5fc9 coremessaging!Microsoft::CoreUI::Dispatch::EventLoop::Callback_RunCoreLoop+0x5c6 0b 00000050`5e67f830 00007ffd`8990c613 coremessaging!Microsoft::CoreUI::Dispatch::EventLoop::Callback_Run+0x9d 0c 00000050`5e67f8a0 00007ffd`8990c522 coremessaging!Microsoft::CoreUI::Registrar::CuiRegistrar::Run+0xdb 0d 00000050`5e67f8f0 00007ffd`8990c46f coremessaging!CoreUIRunRegistrarServer+0xa6 0e 00000050`5e67f9b0 00007ffd`8ed51fe4 coremessaging!CoreUIRegistrarService::RegistrarServerThread+0x3f 0f 00000050`5e67f9e0 00007ffd`8f89ef91 KERNEL32!BaseThreadInitThunk+0x14 10 00000050`5e67fa10 00000000`00000000 ntdll!RtlUserThreadStart+0x21 --- cut --- The actual data (the ALPC message) that was copied to user-mode in our test environment is as follows: --- cut --- 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000010: 02 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 ................ 00000020: a8 00 00 00 aa aa aa aa a8 00 00 00 01 00 0d 00 ................ 00000030: 10 00 00 00 be f5 29 eb 8a e5 e7 11 b5 17 99 31 ......)........1 00000040: df 4f ac 05 88 00 00 00 5c 00 42 00 61 00 73 00 .O......\.B.a.s. 00000050: 65 00 4e 00 61 00 6d 00 65 00 64 00 4f 00 62 00 e.N.a.m.e.d.O.b. 00000060: 6a 00 65 00 63 00 74 00 73 00 5c 00 5b 00 43 00 j.e.c.t.s.\.[.C. 00000070: 6f 00 72 00 65 00 4d 00 73 00 67 00 4b 00 5d 00 o.r.e.M.s.g.K.]. 00000080: 2d 00 7b 00 65 00 62 00 32 00 39 00 66 00 35 00 -.{.e.b.2.9.f.5. 00000090: 62 00 65 00 2d 00 65 00 35 00 38 00 61 00 2d 00 b.e.-.e.5.8.a.-. 000000a0: 31 00 31 00 65 00 37 00 2d 00 62 00 35 00 31 00 1.1.e.7.-.b.5.1. 000000b0: 37 00 2d 00 39 00 39 00 33 00 31 00 64 00 66 00 7.-.9.9.3.1.d.f. 000000c0: 34 00 66 00 61 00 63 00 30 00 35 00 7d 00 00 00 4.f.a.c.0.5.}... --- cut --- The pool allocation from which the 4 uninitialized bytes at offsets 0x24-0x27 originate was requested in win32kbase!CoreMessagingK::Runtime::AllocUninitialized. Based on the contents of the ALPC message data, we suspect that the caller of the allocator a few stack frames higher was win32kbase!CoreMessagingK::SendHost::AllocateBuffer. Unfortunately, we are unable to establish any further details regarding the system state and broader context around the leak. It is not clear if any special privileges need to be held to access the disclosed data. In our case, the process reading from the ALPC port was svchost.exe, but we suspect that more restricted processes could access the affected functionality, too. We are leaving it up to the vendor to determine if the leak can be triggered within the context of a regular system user. This bug is subject to a 90 day disclosure deadline. After 90 days elapse or a patch has been made broadly available, the bug report will become visible to the public. Found by: mjurczyk

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