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CVE-2018-0749 : Détail

CVE-2018-0749

7.8
/
HIGH
0.39%V3
Local
2018-01-02 23:00 +00:00
2018-01-13 09:57 +00:00
CVE.org
NVD

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Descriptions

The Microsoft Server Message Block (SMB) Server in Windows 7 SP1, Windows 8.1 and RT 8.1, Windows Server 2008 SP2 and R2 SP1, Windows Server 2012 and R2, 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 SMB Server handles specially crafted files, aka "Windows 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 7.8 HIGH CVSS:3.0/AV:L/AC:L/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.

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.

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 4.6 AV:L/AC:L/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 : 43517

Date de publication : 2018-01-10 23:00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

Windows: SMB Server (v1 and v2) Mount Point Arbitrary Device Open EoP Platform: Windows 10 1703 and 1709 (seems the same on 7 and 8.1 but not extensively tested) Class: Elevation of Privilege Summary: The SMB server driver (srv.sys and srv2.sys) don't check the destination of a NTFS mount point when manually handling a reparse operation leading to being able to locally open an arbitrary device via an SMB client which can result in EoP. Description: Note before I start event though this involves SMB this is only a local issue, I don't know of anyway to exploit this remotely without being able to run an application on the local machine. NTFS mount points are handled local to the SMB server so that the client does not see them. This is different from NTFS symbolic links which are passed back to the client to deal with. In order to handle the symbolic link case the server calls IoCreateFileEx from Smb2CreateFile passing the IO_STOP_ON_SYMLINK flag which results in the IoCreateFileEx call failing with the STATUS_STOPPED_ON_SYMLINK code. The server can then extract the substitution path from the reparse pointer buffer and either pass the buffer to the client if it's a symbolic link or handle it if it's a mount point. The way the server handles a symbolic link is to recall IoCreateFileEx in a loop (it does check for a maximum iteration count although I'd swear that's a recent change) passing the new substitute path. This is different to how the IO manager would handle this operation. In the IO manager's case the reparse operation is limited to a small subset of device types, such as Disk Volumes. If the new target isn't in the small list of types then the reparse will fail with an STATUS_IO_REPARSE_DATA_INVALID error. However the SMB server does no checks so the open operation can be redirected to any device. This is interesting due to the way in which the device is being opened, it's in a system thread and allows a caller to pass an arbitrary EA block which can be processed by the device create handler. One use for this is being able to the spoof the process ID and session ID accessible from a named pipe using APIs such as GetNamedPipeClientProcessId. Normally to set these values to arbitrary values requires kernel mode access, which the SMB driver provides. While you can open a named pipe via SMB anyway in that case you can't specify the arbitrary values as the driver provides its own to set the computer name accessible with GetNamedPipeClientComputerName. I've not found any service which uses these values for security related properties. Note that both SMBv1 and SMBv2 are vulnerable to the same bug even the code isn't really shared between them. Proof of Concept: I’ve provided a PoC as a C# project. It creates a mount point to \Device and then tries to open the CNG driver directly and via the local share for the drive. 1) Compile the C# project. It will need to grab the NtApiDotNet from NuGet to work. 2) Execute the PoC as a normal user. Expected Result: Both direct and via SMB should fail with STATUS_IO_REPARSE_DATA_INVALID error. Observed Result: The direct open fails with STATUS_IO_REPARSE_DATA_INVALID however the one via SMB fails with STATUS_INVALID_INFO_CLASS which indicates that the CNG driver was opened. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/43517.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_7 >> Version -

Microsoft>>Windows_8.1 >> Version -

Microsoft>>Windows_server_2008 >> Version -

Microsoft>>Windows_server_2008 >> Version r2

Microsoft>>Windows_server_2008 >> Version r2

Microsoft>>Windows_server_2012 >> Version -

Microsoft>>Windows_server_2012 >> Version r2

Microsoft>>Windows_server_2016 >> Version -

Microsoft>>Windows_server_2016 >> Version 1709

References

http://www.securitytracker.com/id/1040096
Tags : vdb-entry, x_refsource_SECTRACK
http://www.securityfocus.com/bid/102355
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/43517/
Tags : exploit, x_refsource_EXPLOIT-DB

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