CVE-2018-8214 : Detail

CVE-2018-8214

7
/
High
44.15%V3
Local
2018-06-14
10h00 +00:00
2018-06-22
07h57 +00:00
CVE.org
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CVE Descriptions

An elevation of privilege vulnerability exists in Windows when Desktop Bridge does not properly manage the virtual registry, aka "Windows Desktop Bridge Elevation of Privilege Vulnerability." This affects Windows Server 2016, Windows 10, Windows 10 Servers. This CVE ID is unique from CVE-2018-8208.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE Other No informations.

Metrics

Metrics Score Severity CVSS Vector Source
V3.0 7 HIGH CVSS:3.0/AV:L/AC:H/PR:L/UI:N/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

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.

High

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 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.

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

 nvd@nist.gov
V2 6.9 AV:L/AC:M/Au:N/C:C/I:C/A:C nvd@nist.gov

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 : 44915

Publication date : 2018-06-19 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

Windows: Windows: Desktop Bridge Virtual Registry CVE-2018-0880 Incomplete Fix EoP Platform: Windows 1709 (not tested earlier version) Class: Elevation of Privilege Summary: The handling of the virtual registry for desktop bridge applications can allow an application to create arbitrary files as system resulting in EoP. This is because the fix for CVE-2018-0880 (MSRC case 42755) did not cover all similar cases which were reported at the same time in the issue. Description: Looking at the fix for CVE-2018-0880 the Cache directory and sub files are now secured so only admins and system can access them. This breaks my original PoC but it doesn’t fix the issue. In my original report I also noted that User.dat and UserClasses.dat could also be abused in the same way and those files exist in the Helium directory above the Cache. Therefore the exact same attack can be employed on the Helium directory instead of the Cache directory. To be honest I’m not even convinced that locking down the security on the Cache directory is a robust fix. As we have FILE_DELETE_CHILD access on the Helium directory we could always rename the Cache folder and the activator will recreate it for us. With a bit of effort we could mount the original attack through things like holding a reference to one of the files with WRITE_DAC permissions and race the security descriptor checks in DAXEXEC!OfflineRegistry::EnsureCacheIsSafe. It’d be slightly more work but not unduly so. IMO the only real way to fix this issue would be completely remove the opportunity to replace the registry cache files from a normal user, perhaps by placing them in a secondary location on the system such as under a secured directory in c:\ProgramData. I also haven’t bothered to check if you’ve fixed the read issue that I also reported as part of case 42755. I’ve no reason to believe you have based on what I can see in the code. Proof of Concept: I’ve provided a PoC as a C# project. In order for the exploit to work you need a copy of the Get Office/My Office application installed (I tested with version 17.8830.7600.0). It could be any desktop bridge application however as you just need to run a program inside the container although for that to work some strings in the poc would need to be changed. 1) Compile the C# project. It will need to grab the NtApiDotNet from NuGet to work. 2) Start the poc. It should print that it successfully created the badgers.dll file in system32. The exploit works as follows: * The Helium folder is renamed to Helium-X. * The Helium folder is recreated as a mount point which redirects to the object manager directory \RPC Control * Symbolic links are dropped for the registry hive files. The LOG files are redirected to an arbitrary name in the windows folder. Note that the PoC will leave the user profile for the Office Hub application broken, you should delete the fake Helium folder and rename the Helium-X folder to try the exploit again. Expected Result: The application creation fails or at least the symbolic links aren’t followed. Observed Result: The file badgers.dll is created in the system32 folder which is writable by a normal user. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/44915.zip

Products Mentioned

Configuraton 0

Microsoft>>Windows_10 >> Version 1607

Microsoft>>Windows_10 >> Version 1703

Microsoft>>Windows_10 >> Version 1709

Microsoft>>Windows_10 >> Version 1803

Configuraton 0

Microsoft>>Windows_server_2016 >> Version -

Microsoft>>Windows_server_2016 >> Version 1709

Microsoft>>Windows_server_2016 >> Version 1803

References

https://www.exploit-db.com/exploits/44915/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securityfocus.com/bid/104394
Tags : vdb-entry, x_refsource_BID
http://www.securitytracker.com/id/1041093
Tags : vdb-entry, x_refsource_SECTRACK