CVE-2019-0566 : Detail

CVE-2019-0566

8.8
/
High
Authorization problems
A01-Broken Access Control
27.85%V3
Network
2019-01-08
20h00 +00:00
2019-01-15
09h57 +00:00
CVE.org
NVD
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CVE Descriptions

An elevation of privilege vulnerability exists in Microsoft Edge Browser Broker COM object, aka "Microsoft Edge Elevation of Privilege Vulnerability." This affects Microsoft Edge.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-862 Missing Authorization
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Metrics

Metrics Score Severity CVSS Vector Source
V3.0 8.8 HIGH CVSS:3.0/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

A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from 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 against 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 to carry out an attack.

User Interaction

This metric captures the requirement for a 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

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.

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 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 that one has in the description of a vulnerability.

Environmental Metrics

 [email protected]
V2 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P [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 : 46161

Publication date : 2019-01-13 23h00 +00:00
Author : Google Security Research
EDB Verified : Yes

Windows: Browser Broker Cross Session EoP Platform: Windows 10 1803 (not tested anything else). Class: Elevation of Privilege Security Boundary (per Windows Security Service Criteria): Session Boundary Summary: The Browser Broker COM object doesn’t verify its caller correctly allowing one user to execute arbitrary code in another logged on user’s session. Description: The Browser Broker Class (CLSID: 0002df02-0000-0000-c000-000000000046) is closely tied with Microsoft Edge and is used to perform certain privileged operations that the main browser process running in an App Container cannot do. The majority of the calls are checked with functions such as BrokerAuthenticateAttachedCallerGetPIC which ensures the caller is an Edge process (based on its package ID) and meets certain requirements based on the sandbox type etc. One thing this code doesn’t do is check that the caller is the same user as the running broker process. As the user is not checked this means it’s only the COM security which prevents you instantiating this in another running session on the same machine. The COM users allowed to launch the broker are: * Everyone * microsoft.microsoftedge_8wekyb3d8bbwe (package SID) This means that everyone is allowed to start the broker COM process even in another session. However perhaps the access permissions will save us: * NT AUTHORITY\Authenticated Users * BUILTIN\Guests * microsoft.microsoftedge_8wekyb3d8bbwe (package SID) * NAMED CAPABILITIES\Lpac Web Platform Even Guests can access the COM object after creating it (I’ve no idea why of all things). Basically though these sets of permissions ensure that one user can create and call methods on the broker in another session. The only requirement is you need to impersonate the Microsoft Edge token when calling methods, but that’s easy to get just by stealing the token from a running Edge process. Once you’ve got access to the broker COM server it’s pretty easy to exploit to get arbitrary code execution. You can modify files through the IFileOperationBroker or just call ShellExecute using IDownloadExecutionBroker. Ultimately I warned you after cases 36544 and 37954 that you should be fixing the root cause of normal user’s being able to use the Session Moniker not playing whack-a-mole with COM objects. Of course you didn’t listen then and no doubt you’ll just try and fix browser broker and be done with it. This issue also demonstrates that the Browser Broker is an easy sandbox escape if you can get into the MicrosoftEdge process, which doesn’t seem a good thing IMO. While LPAC certainly makes it harder to elevate to the main browser process I’d not be confident of it being a complete security boundary. Proof of Concept: I’ve provided a PoC as a C++ project. It will steal the access token from a running copy of Edge then restart itself in another logged on session. 1) Compile the C++ project. 2) Ensure there’s two users logged on to the same system. 3) Start Edge in the session you’ll run the PoC from. 4) Run the PoC. Expected Result: Create a broker and accessing it in another session should fail. Observed Result: The PoC is running in another user’s session. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46161.zip

Products Mentioned

Configuraton 0

Microsoft>>Edge >> Version -

Microsoft>>Windows_10 >> Version -

Microsoft>>Windows_10 >> Version 1607

Microsoft>>Windows_10 >> Version 1703

Microsoft>>Windows_10 >> Version 1709

Microsoft>>Windows_10 >> Version 1803

Microsoft>>Windows_10 >> Version 1809

Microsoft>>Windows_server_2016 >> Version -

Microsoft>>Windows_server_2019 >> Version -

References

http://www.securityfocus.com/bid/106417
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/46161/
Tags : exploit, x_refsource_EXPLOIT-DB