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CVE-2018-0822 : Détail

CVE-2018-0822

7
/
HIGH
0.26%V3
Local
2018-02-12 23:00 +00:00
2018-02-22 09:57 +00:00
CVE.org
NVD

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Descriptions

NTFS in Windows 10 Gold, 1511, 1607, 1703 and 1709, Windows Server 2016 and Windows Server, version 1709 allows an elevation of privilege vulnerability due to the way NTFS handles objects, aka "Windows NTFS Global Reparse Point Elevation of Privilege Vulnerability".

Informations

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE Other No informations.

Metrics

Metric Score Sévérité CVSS Vecteur 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

 [email protected]
V2 4.4 AV:L/AC:M/Au:N/C:P/I:P/A:P [email protected]

EPSS

EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.

EPSS Score

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

EPSS Percentile

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
EPSS First.org

Informations sur l'Exploit

Exploit Database EDB-ID : 44147

Date de publication : 2018-02-19 23:00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

Windows: Global Reparse Point Security Feature Bypass/Elevation of Privilege Platform: Windows 10 1709 (functionality not present prior to this version) Class: Security Feature Bypass/Elevation of Privilege Summary: It’s possible to use the new Global Reparse Point functionality introduced in Windows 10 1709 to bypass the existing sandbox limitations of creating arbitrary file symbolic links. Description: Windows 10 introduced mitigations to prevent the abuse of various types of symbolic links when a process is running in a sandbox. This is a combination of outright blocking of the functionality (such as in the case of Registry Key symlinks) to doing checks on the target location so that the sandbox user can write to the location (in the case of Mount Points). Fall Creator’s Update has introduced a new defined reparse tag, the Global Reparse Point (value 0xA0000019) which I assume is for Silo’s where a symlink can be added into the Silo’s visible namespaces which actually redirects to the global namespace. One user of this is the named pipe file system. It seems that nothing prevents you creating this type of reparse point on an NTFS volume, it doesn’t get checked by the kernel for the sandbox mitigation and because the NTFS driver ignores anything which isn’t a mount point or a ntfs symbolic link it will also not check for the SeCreateSymbolicLinkPrivilege. This symbolic link type works to reparse to any file type so you can create either a file or directory symbolic link. The reparse buffer is basically the same as the normal symbolic link one, but with a different tag. In fact strangely the named pipe file system passes back a buffer with the normal symbolic link tag but with the global reparse tag in the data structure passed back to IopParseDevice. Outside of the behavior in sandboxes you might want to check that the reparse buffer is correctly verified. Normally the NTFS driver checks the structure of a reparse buffer using FsRtlValidateReparsePointBuffer but that function doesn’t know about the new reparse tag, so you could end up with completely untrusted data being passed into the object manager (NPFS synthesizes the reparse buffer so normally it would be trusted). I’ve not checked if you could trivially BSoD the machine through this approach. Note that while NTFS symbolic links can be created without privileges in developer mode this bypass also allows a normal user to create them without developer mode being enabled so also acts as an EoP. Proof of Concept: I’ve provided a PoC as a C# project. 1) Compile the C# project. It will need to grab the NtApiDotNet from NuGet to work. 2) Run the poc as Low IL or an in AC passing on the command line the name of the symlink file to create and a target path. For example ‘poc c:\test\hello c:\windows’ will create a symlink ‘hello’ pointing at ‘c:\windows’. Make sure the destination name can be written to as the sandboxed user. 3) Open the symbolic link as a normal privileged user to see if the reparse target is followed. Expected Result: The creation of the symlink should fail with an error. Observed Result: The symlink is created, is valid and can be used to access the target. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/44147.zip

Products Mentioned

Configuraton 0

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_server_2016 >> Version -

Microsoft>>Windows_server_2016 >> Version 1709

References

http://www.securityfocus.com/bid/102942
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/44147/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securitytracker.com/id/1040378
Tags : vdb-entry, x_refsource_SECTRACK

Plus d'informations
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