CVE-2018-0748 : Détail

CVE-2018-0748

7.8
/
Haute
Improper Privilege Management
A04-Insecure Design
76.63%V3
Local
2018-01-04
14h00 +00:00
2024-09-16
23h25 +00:00
CVE.org
NVD
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Descriptions du CVE

The Windows kernel 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 memory addresses are handled, aka "Windows Elevation of Privilege Vulnerability".

Informations du CVE

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE-269 Improper Privilege Management
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

Métriques

Métriques Score Gravité 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.

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.
EPSS First.org

Informations sur l'Exploit

Exploit Database EDB-ID : 43514

Date de publication : 2018-01-10 23h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

/* Windows: NTFS Owner/Mandatory Label Privilege Bypass EoP Platform: Windows 10 1709 not tested 8.1 Update 2 or Windows 7 Class: Elevation of Privilege Summary: When creating a new file on an NTFS drive it’s possible to circumvent security checks for setting an arbitrary owner and mandatory label leading to a non-admin user setting those parts of the security descriptor with non-standard values which could result in further attacks resulting EoP. Description: The kernel limits who can arbitrarily set the Owner and Mandatory Label fields of a security descriptor. Specifically unless the current token has SeRestorePrivilege, SeTakeOwnershipPrivilege or SeRelabelPrivilege you can only set an owner which is set in the current token (for the label is can also be less than the current label). As setting an arbitrary owner in the token or raising the IL is also a privileged operation this prevents a normal user from setting these fields to arbitrary values. When creating a new file on an NTFS volume you can specify an arbitrary Security Descriptor with the create request and it will be set during the creation process. If you specify an arbitrary owner or label it will return an error as expected. Looking at the implementation in NTFS the function NtfsCreateNewFile calls NtfsAssignSecurity which then calls the kernel API SeAssignSecurityEx. The problem here is that SeAssignSecurityEx doesn’t take an explicit KPROCESSOR_MODE argument so instead the kernel takes the current thread’s previous access mode. The previous mode however might not match up with the current assumed access mode based on the caller, for example if the create call has been delegated to a system thread. A common place this mode mismatch occurs is in the SMB server, which runs entirely in the system process. All threads used by SMB are running with a previous mode of KernelMode, but will create files by specifying IO_FORCE_ACCESS_CHECK so that the impersonated caller identity is used for security checks. However if you specify a security descriptor to set during file creation the SMB server will call into NTFS ending up in SeAssignSecurityEx which then thinks it’s been called from KernelMode and bypasses the Owner/Label checks. Is this useful? Almost certainly there’s some applications out there which use the Owner or Label as an indicator that only an administrator could have created the file (even if that’s not a very good security check). For example VirtualBox uses it as part of its security checks for whether a DLL is allowed to be loaded in process (see my blog about it https://googleprojectzero.blogspot.com.au/2017/08/bypassing-virtualbox-process-hardening.html) so I could imagine other examples including Microsoft products. Another example is process creation where the kernel checks the file's label to determine if it needs to drop the IL on the new process, I don't think you can increase the IL but maybe there's a way of doing so. Based on the implementation this looks like it would also bypass the checks for setting the SACL, however due to the requirement for an explicit access right this is blocked earlier in the call through the SMBv2 client. I’ve not checked if using an alternative SMBv2 client implementation such as SAMBA would allow you to bypass this restriction or whether it’s still blocked in the server code. It’s hard to pin down which component is really at fault here. It could be argued that SeAssignSecurityEx should take a KPROCESSOR_MODE parameter to determine the security checks rather than using the thread’s previous mode. Then again perhaps NTFS needs to do some pre-checking of it’s own? And of course this wouldn’t be an issue if the SMB server driver didn’t run in a system thread. Note this doesn’t bypass changing the Owner/Label of an existing file, it’s only an issue when creating a new file. Proof of Concept: I’ve provided a PoC as a C# source code file. You need to compile it first. It will attempt to create two files with a Security Descriptor with the Owner set to SYSTEM. 1) Compile the C# source code file. 2) Execute the PoC as a normal user or at least a filtered split-token admin user. Expected Result: Both file creations should fail with the same error when setting the owner ID. Observed Result: The first file which is created directly fails with an error setting the owner ID. The second file which is created via the C$ admin share on the local SMB server succeeds and if the SD is checked the owner is indeed set to SYSTEM. */ using System; using System.IO; using System.Security.AccessControl; namespace NtfsSetOwner_EoP { class Program { static void CreateFileWithOwner(string path) { try { FileSecurity sd = new FileSecurity(); sd.SetSecurityDescriptorSddlForm("O:SYG:SYD:(A;;GA;;;WD)"); using (var file = File.Create(path, 1024, FileOptions.None, sd)) { Console.WriteLine("Created file {0}", path); } } catch (Exception ex) { Console.WriteLine("Error creating file {0} with arbitrary owner", path); Console.WriteLine(ex.Message); } } static void Main(string[] args) { try { Directory.CreateDirectory(@"c:\test"); CreateFileWithOwner(@"c:\test\test1.txt"); CreateFileWithOwner(@"\\localhost\c$\test\test2.txt"); } catch (Exception ex) { Console.WriteLine(ex); } } } }

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

Références

https://www.exploit-db.com/exploits/43514/
Tags : exploit, x_refsource_EXPLOIT-DB
http://www.securityfocus.com/bid/102354
Tags : vdb-entry, x_refsource_BID
http://www.securitytracker.com/id/1040095
Tags : vdb-entry, x_refsource_SECTRACK