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CVE-2018-8134 : Detail

CVE-2018-8134

7
/
HIGH
0.11%V3
Local
2018-05-09 17:00 +00:00
2018-05-19 07:57 +00:00
CVE.org
NVD

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Descriptions

An elevation of privilege vulnerability exists in the way that the Windows Kernel API enforces permissions, aka "Windows Elevation of Privilege Vulnerability." This affects Windows Server 2012 R2, Windows RT 8.1, Windows Server 2016, Windows 8.1, Windows 10, Windows 10 Servers.

Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE Other No informations.

Metrics

Metric 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 : 44630

Publication date : 2018-05-15 22:00 +00:00
Author : Google Security Research
EDB Verified : Yes

Windows: Token Trust SID Access Check Bypass EOP Platform: Windows 10 1709 (also tested current build of RS4) Class: Elevation of Privilege Summary: A token’s trust SID isn’t reset when setting a token after process creation allowing a user process to bypass access checks for trust labels. Description: When a protected process is created it sets the protection inside the EPROCESS structure but also adds a special trust SID to the primary token as part of SeSubProcessToken. Where the process protection is used for things such as what access rights to other processes the trust SID is used for direct access checks where a security descriptor has a process trust label. A good example is the \KnownDlls object directory which is labeled as PPL-WinTcb to prevent tampering from anything not at that protection level. This trust SID isn’t cleared during duplication so it’s possible for a non-protected process to open the token of a protected process and duplicate it with the trust SID intact. However using that token should clear the SID, or at least cap it to the maximum process protection level. However there’s a missing edge case, when setting a primary token through NtSetInformationProcess (specifically in PspAssignPrimaryToken). Therefore we can exploit this with the following from a normal non-admin process: 1) Create a protected process, werfaultsecure.exe is a good candidate as it’ll run PP-WinTcb. It doesn’t have to do anything special, just be created. 2) Open the process token (we get PROCESS_QUERY_LIMITED_INFORMATION) and duplicate it to a new primary token. 3) Create a new suspended process which will run the exploit code with the original token. 4) Set the protected process token using NtSetInformationProcess 5) Resume exploit process and do something which needs to pass the trust label check. NOTE: There is also a related issue during impersonation and the call to SeTokenCanImpersonate. Normally the current process trust SID is checked against the impersonation token trust SID and if the process token’s is lower a flag is returned to the caller which resets the new token’s trust SID to the process one. This check occurs before the check for SeImpersonatePrivilege but _after_ the check for an anonymous token authentication ID. Therefore if you’re an admin you could craft a token with the anonymous token authentication ID (but with actual groups) and do a similar trick as with the process token to prevent the reset of the trust SID during impersonation. However I couldn’t find an obvious use for this as the trust label seems to be based on the minimum between the impersonation and process token’s trust SIDs and when impersonating over a boundary such as in RPC it looks like it gets reset to the process’ protection level. But might be worth cleaning this up as well if you’re there. Proof of Concept: I’ve provided a PoC as a C# project. It does the previous described trick to run a process which can then set the trust label on a new event object it creates (\BaseNamedObject\PPDEMO). If you run the poc with a command line parameter it will try and do the event creation but should print access denied. 1) Compile the C# project. It will need to grab the NtApiDotNet from NuGet to work. 2) Run the poc with no parameters as a normal user. It will capture the token and respawn itself to create the event. Expected Result: Setting the trust label returns access denied. Observed Result: The trust label is successfully set. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/44630.zip

Products Mentioned

Configuraton 0

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_7 >> Version *

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

Microsoft>>Windows_server_2016 >> Version 1803

References

http://www.securitytracker.com/id/1040849
Tags : vdb-entry, x_refsource_SECTRACK
https://www.exploit-db.com/exploits/44630/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securityfocus.com/bid/104041
Tags : vdb-entry, x_refsource_BID

More information
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