CVE-2019-0836 : Détail

CVE-2019-0836

7.8
/
Haute
75.89%V3
Local
2019-04-09
18h16 +00:00
2019-04-17
00h06 +00:00
CVE.org
NVD
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Descriptions du CVE

An elevation of privilege vulnerability exists when Windows improperly handles calls to the LUAFV driver (luafv.sys), aka 'Windows Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-0730, CVE-2019-0731, CVE-2019-0796, CVE-2019-0805, CVE-2019-0841.

Informations du CVE

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state.

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 : 46718

Date de publication : 2019-04-15 22h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

Windows: LUAFV PostLuafvPostReadWrite SECTION_OBJECT_POINTERS Race Condition EoP Platform: Windows 10 1809 (not tested earlier) Class: Elevation of Privilege Security Boundary (per Windows Security Service Criteria): User boundary Summary: The LUAFV driver has a race condition in the LuafvPostReadWrite callback if delay virtualization has occurred during a read leading to the SECTION_OBJECT_POINTERS value being reset to the underlying file resulting in EoP. Description: NOTE: While it has a similar effect as issue 49960 I believe it is a different root cause which might still be exploitable after any fixes. This bug is actually worse than 49960 as you can modify the original file rather than just the cached data and you can do it to any file which can be virtualized as you don’t need to have a file which has a NULL CONTROL_AREA pointer. When a IRP_MJ_READ request is issued to a delay virtualized file the filter driver first calls LuafvPreRedirectWithCallback which determines if the file is virtualized, it then sets the underlying, read-only file as the target file object for the filter processing as well as storing the file object in the completion context. When the read operation completes the LuafvPostReadWrite method is called which will inspect the completion context and copy out the file position and the SECTION_OBJECT_POINTERS value. As there’s no locking in place at this point if the file delay virtualization is completed between the call to LuafvPreRedirectWithCallback and LuafvPostReadWrite then the SECTION_OBJECT_POINTERS and cache from the read-only file is used to overwrite the top-level “fake” file object, even though LuafvPerformDelayedVirtualization would have changed them to the new read-write virtual store file. By exploiting this race it’s possible to map the “real” file read-write which allows you to modify the data (you can probably also just write to the underlying file as well). The trick to exploiting this bug is winning the race. One behavior that makes it an easy race to win is the delayed virtualization process passes on almost all CreateOptions flags to the underlying file create calls. By passing the FILE_COMPLETE_IF_OPLOCKED flag you can bypass waiting for an oplock break on IRP_MJ_CREATE and instead get it to occur on IRP_MJ_READ. The following is a rough overview of the process: 1) Open a file which will be delay virtualized and oplock with READ/HANDLE lease. 2) Open the file again for read/write access which will be delay virtualized. Pass the FILE_COMPLETE_IF_OPLOCKED flag to the create operation. The create operation will return STATUS_OPLOCK_BREAK_IN_PROGRESS but that’s a success code so the delayed virtualization setup is successful. 3) Create a new dummy file in the virtual store to prevent the driver copying the original data (which will likely wait for an oplock break). 4) Issue a read request on the virtualized file object, at this point the IRP_MJ_READ will be dispatched to “real” file and will get stuck waiting for an oplock break inside the NTFS driver. 5) While the read request is in progress issue a IRP_MJ_SET_EA request, this operation is ignored for oplock breaks so will complete, however the LUAFV driver will call LuafvPreWrite to complete the delayed virtualization process. 6) Close the acknowledge the oplock break by closing the file opened in 1. 7) Wait for read operation to complete. 8) Map the file as a read/write section. The data should be the “real” file contents not the dummy virtual store contents. Modifying the file will now cause the “real” file to be modified. Note that even if you filtered the CreateOptions (as you should IMO) the race still exists, it would just be harder to exploit. Fixing wise, you probably want to check the virtualized object context and determine that the the delay virtualization has already occurred before overwriting anything in the top-level file object. These operations can’t be done from any sandbox that I know of so it’s only a user to system privilege escalation. Proof of Concept: I’ve provided a PoC as a C# project. It will map the license.rtf file as read-write, although it won’t try and modify the data. However if you write to the mapped section it will change the original file. 1) Compile the C# project. It’ll need to pull NtApiDotNet from NuGet to build. 2) As a normal user run the PoC. 3) The PoC should print the first 16 characters of the mapped file. Expected Result: The mapped data should be all ‘A’ characters. Observed Result: The mapped data is the actual license.rtf file and it’s mapped writable. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46718.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_10 >> Version 1809

Microsoft>>Windows_7 >> Version -

Microsoft>>Windows_8.1 >> Version -

Microsoft>>Windows_rt_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

Microsoft>>Windows_server_2016 >> Version 1803

Microsoft>>Windows_server_2019 >> Version -

Références

http://www.securityfocus.com/bid/107719
Tags : vdb-entry, x_refsource_BID
https://www.exploit-db.com/exploits/46718/
Tags : exploit, x_refsource_EXPLOIT-DB