CVE-2018-0823 : Détail

CVE-2018-0823

7
/
Haute
48.11%V3
Local
2018-02-15
02h00 +00:00
2024-09-16
19h21 +00:00
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Descriptions du CVE

The Named Pipe File System in Windows 10 version 1709 and Windows Server, version 1709 allows an elevation of privilege vulnerability due to the way the Named Pipe File System handles objects, aka "Named Pipe File System Elevation of Privilege Vulnerability".

Informations du CVE

Faiblesses connexes

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

Métriques

Métriques Score Gravité 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.

Score EPSS

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.

Percentile EPSS

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.

Informations sur l'Exploit

Exploit Database EDB-ID : 44148

Date de publication : 2018-02-19 23h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

Windows: NPFS Symlink Security Feature Bypass/Elevation of Privilege/Dangerous Behavior Platform: Windows 10 1709 (functionality not present prior to this version) Class: Security Feature Bypass/Elevation of Privilege/Dangerous Behavior Summary: It’s possible to create NPFS symlinks as a low IL or normal user and the implementation doesn’t behave in a similar manner to other types of Windows symlinks leading to dangerous behavior or EoP. Description: Windows 10 1709 introduced a new symlink feature to NPFS which is accessible from a FSCTL. From what I can see the implementation has a number of security issues which concern me: 1) Creation of symbolic links is only limited to a user which can open the root named pipe device. I.e. \Device\NamedPipe. This users which can open the device includes restricted tokens with the RESTRICTED SID and Low IL tokens. 2) Accessing a symlink results in the NPFS driver synthesizing a NTFS symlink reparse point which is passed back to the object manager. This allows the symlink to reparse to different devices. This is presumably by design but it’s dangerous behavior. 3) Opening a symlink doesn’t respect the FILE_OPEN_REPARSE_POINT which could lead to some unusual behavior. The fact that you can create the symlink as a lower privileged user is bad enough, although I don’t believe it can be done from an AC so maybe you don’t care about it. But the other two issues are examples of dangerous behavior which _will_ come back to bite you at some point in the future. Let’s take point 2 as an example, up to this point NPFS hasn’t had the concept of symbolic links. Sure you could drop an appropriate object manager symlink somewhere and get a caller to follow it but you’d need to be able to influence the callers path or their DOS device directory. With this if a privileged caller is expecting to open a named pipe, say \\.\pipe\ABC then ABC could actually be a symbolic link to a normal file. If the caller then just writes data to the pipe expecting it to be a stream they could actually be writing data into a file which might result in EoP. Basically I see it’s a case of when not if that a EoP bug is found which abuses this behavior. Also, there’s no way I know of for detecting you’re opening a symbolic link. For example if you open the target with the FILE_OPEN_REPARSE_POINT flag it continues to do the reparse operation. Due to creating a normal NTFS symbolic link this might also have weird behavior when a remote system accessed a named pipe, although I’ve not tested that. Overall I think the behavior of the implementation has the potential for malicious use and should be limited to privileged users. I don’t know it’s original purpose, perhaps it’s related to Silos (there is a flag to make a global symlink) or it’s to make it easier to implement named pipes in WSL, I don’t know. If the purpose is just to symlink between named pipes then perhaps only allow a caller to specify the name relative to the NPFS device rather than allowing a full object path. Proof of Concept: I’ve provided a PoC as a C# project. The PoC will create a symlink called ABC which points to notepad.exe. It will check the file file it opens via the symlink matches the file opened directly. 1) Compile the C# project. It will need to grab the NtApiDotNet from NuGet to work. 2) Run the poc as Low IL (using say psexec). Expected Result: The creation of the symlink should fail with an error. Observed Result: The symlink is created, is valid and the poc printed ‘Success’ as it’s opened the copy of notepad.exe via the symlink. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/44148.zip

Products Mentioned

Configuraton 0

Microsoft>>Windows_10 >> Version 1709

Microsoft>>Windows_server_2016 >> Version 1709

Références

http://www.securitytracker.com/id/1040379
Tags : vdb-entry, x_refsource_SECTRACK
https://www.exploit-db.com/exploits/44148/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securityfocus.com/bid/102919
Tags : vdb-entry, x_refsource_BID