CVE-2018-0986 : Detail

CVE-2018-0986

8.8
/
High
Overflow
88.74%V3
Network
2018-04-04
15h00 +00:00
2018-04-11
22h57 +00:00
CVE.org
NVD
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CVE Descriptions

A remote code execution vulnerability exists when the Microsoft Malware Protection Engine does not properly scan a specially crafted file, leading to memory corruption, aka "Microsoft Malware Protection Engine Remote Code Execution Vulnerability." This affects Windows Defender, Windows Intune Endpoint Protection, Microsoft Security Essentials, Microsoft System Center Endpoint Protection, Microsoft Exchange Server, Microsoft System Center, Microsoft Forefront Endpoint Protection.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-787 Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 8.8 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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.

Network

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).

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 when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.

User Interaction

This metric captures the requirement for a human 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

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

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 a 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.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

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 in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

 [email protected]
V2 9.3 AV:N/AC:M/Au:N/C:C/I:C/A:C [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 : 44402

Publication date : 2018-04-04 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

Windows Defender inspects a variety of different archive formats, among others RAR. Inspection of mpengine.dll revealed that the code responsible for processing RAR archives appears to be a forked and modified version of the original unrar code; given that it still processes the VMSF_UPCASE filter (which was removed in unrar 5.0), it seems that the code is derived from a version of unrar older or equal than 4.2.4. Interestingly, the issue discovered in CVE-2012-6706 (Sophos VMSF_DELTA, and in 2017 unrar) and other signedness issues in the RarVM::ExecuteStandardFilter function were fixed long ago (apparently without a report to upstream, most likely by simply turning the relevant variables from "signed" to "unsigned"). It appears that this blanket conversion from signed to unsigned ended up introducing a new vulnerability, though: From unrar 4.2.4 rarvm.cpp: case VMSF_RGB: { int DataSize=R[4],Width=R[0]-3,PosR=R[1]; byte *SrcData=Mem,*DestData=SrcData+DataSize; const int Channels=3; SET_VALUE(false,&Mem[VM_GLOBALMEMADDR+0x20],DataSize); if ((uint)DataSize>=VM_GLOBALMEMADDR/2 || PosR<0) break; for (int CurChannel=0;CurChannel<Channels;CurChannel++) The code clearly ensures that PosR is positive from here on. This check is no longer present in the binary version of the same code in mpengine, most likely since most signed comparisons in this function have been turned unsigned. This causes a vulnerability later in the same function (RarVM::ExecuteStandardFilter) Decompile of the mpengine code snippet: if ( PosR + 2 < DataSize ) { v50 = (_BYTE *)(v39 + PosR); do { v51 = v50[1]; *v50 += v51; v50 += 3; *(v50 - 1) += v51; } while ( (unsigned int)&v50[2 - v39] < DataSize ); Original unrar code: for (int I=PosR,Border=DataSize-2;I<Border;I+=3) { byte G=DestData[I+1]; DestData[I]+=G; DestData[I+2]+=G; } An attacker that can set PosR to be -2, and DataSize to 1, will bypass the (PosR + 2 < DataSize) check. v50 above will then point to one byte *before* the allocated buffer (v50 respective DestData points into a buffer at index DataSize -- so adding -2 to index 1 will index to -1. The byte from the start of this array will be added into the byte preceding the array. A minimal sample RAR file that exhibits these traits & causes mpengine to corrupt memory and crash is attached. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/44402.zip

Products Mentioned

Configuraton 0

Microsoft>>Exchange_server >> Version 2013

Microsoft>>Exchange_server >> Version 2016

Microsoft>>Security_essentials >> Version -

Configuraton 0

Microsoft>>Forefront_endpoint_protection_2010 >> Version -

Microsoft>>Intune_endpoint_protection >> Version -

Microsoft>>System_center_endpoint_protection >> Version *

Microsoft>>System_center_endpoint_protection >> Version 2012

Microsoft>>System_center_endpoint_protection >> Version 2012

Configuraton 0

Microsoft>>Windows_defender >> Version -

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_7 >> Version -

Microsoft>>Windows_8.1 >> Version *

Microsoft>>Windows_rt_8.1 >> Version *

Microsoft>>Windows_server_2008 >> Version r2

Microsoft>>Windows_server_2012 >> Version *

Microsoft>>Windows_server_2012 >> Version r2

Microsoft>>Windows_server_2016 >> Version *

Microsoft>>Windows_server_2016 >> Version 1709

References

http://www.securitytracker.com/id/1040631
Tags : vdb-entry, x_refsource_SECTRACK
http://www.securityfocus.com/bid/103593
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/44402/
Tags : exploit, x_refsource_EXPLOIT-DB