CVE-2015-7358 Détail

CVE-2015-7358

Score / Gravité

7.8

Haute

OWSAP

A01-Broken Access Control

EPSS

0.06%V3

Vecteur

Local

Publié

2017-10-02
17h00 +00:00

Modifié

2017-10-02
16h57 +00:00

Liens officiels

CVE.org

NVD

Notifications pour un CVE

Restez informé de toutes modifications pour un CVE spécifique.

Gestion des notifications

Liste des Notifications

Notifications pour un CVE

Restez informé de toutes modifications pour un CVE spécifique.

Critères appliqués l'envoi de l'alerte : par rapport à la dernière alerte envoyée + différences au niveau de CISA, EPSS, CVSS, CWE, Solutions, CPE.

Paramètres

Vous pouvez spécifier un titre qui sera récupéré dans les alertes qui seront envoyées.

Spécifiez ici un CVE ID comme CVE-2025-1234

Planifications

Mois

Prochaine exécution calculée

Jour

Jour de la semaine

Heure

Minute

Date de création

Dernière exécution

Prochaine exécution

Fonctionnalité nécessitant une connexion

Cette fonctionnalité qui vous permet de recevoir des alertes, n'est active que lorsque vous êtes connecté à votre compte.

Descriptions du CVE

The IsDriveLetterAvailable method in Driver/Ntdriver.c in TrueCrypt 7.0, VeraCrypt before 1.15, and CipherShed, when running on Windows, does not properly validate drive letter symbolic links, which allows local users to mount an encrypted volume over an existing drive letter and gain privileges via an entry in the /GLOBAL?? directory.

Informations du CVE

Faiblesses connexes

CWE-ID	Nom de la faiblesse	Source
CWE-264	Category : Permissions, Privileges, and Access Controls Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.

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 More informations 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	7.2		AV:L/AC:L/Au:N/C:C/I:C/A:C	[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 : 38403

Date de publication : 2015-10-04 22h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

Source: https://code.google.com/p/google-security-research/issues/detail?id=538 Truecrypt 7 Derived Code/Windows: Drive Letter Symbolic Link Creation EoP Platform: Windows Class: Local Elevation of Privilege Tested on: VeraCrypt 1.13 x86 on Windows 10 Summary: The Windows driver used by projects derived from Truecrypt 7 (verified in Veracrypt and CipherShed) are vulnerable to a local elevation of privilege attack by abusing the drive letter symbolic link creation facilities to remap the main system drive. With the system drive remapped it’s trivial to get a new process running under the local system account. Description: Any user on the system can connect to the Truecrypt device object and mount a new encrypted volume. As part of this process the driver will try and create the requested drive letter by calling IoCreateSymbolicLink. To prevent redefining an existing drive letter a call is made to IsDriveLetterAvailable which attempts to open the link “\DosDevices\X:” for reading, returning FALSE if it was successfully opened. The specific code in src\Driver\Ntdriver.c is: if (NT_SUCCESS (ZwOpenSymbolicLinkObject (&handle, GENERIC_READ, &objectAttributes))) { ZwClose (handle); return FALSE; } return TRUE; The bug which allows you to bypass this is due to the use of the NT_SUCCESS macro. This means that any error opening the symbolic link will cause the drive letter to be assumed to not exist. If we can cause the open to fail in any way then we can bypass this check and mount the volume over an existing drive letter. This is possible because with terminal services support the \DosDevices path points to a special fake path \?? which first maps to a per-user writable location (under \Sessions\0\DosDevices) before falling back to \GLOBAL??. When the kernel creates a new object under \?? is creates it in the per-user location instead so there’s no conflict with a drive symbolic link in \GLOBAL??. So how to bypass the check? The simplest trick is to just create any other type of object with that name, such as an object directory. This will cause ZwOpenSymbolicLink to fail with STATUS_OBJECT_TYPE_MISMATCH passing the check. This in itself would only cause problems for the current user if it wasn’t for the fact that there exists a way of replacing the current processes device map directory using the NtSetInformationProcess system call. You can set any object directory to this which allows you DIRECTORY_TRAVERSE privilege, which is pretty much anything. In particular we can set the \GLOBAL?? directory itself. So to exploit this and remap the C: drive to the truecrypt volume we do the following: 1) Set the current process’s device map to a new object directory. Create a new object called C: inside the device map directory. 2) Mount a volume (not using the mount manager) and request the C: drive mapping. The IsDriveLetterAvailable will return TRUE. 3) Wait for the driver to open the volume and at that point delete the fake C: object (if we don’t do this then the creation will fail). While this looks like a race condition (which you can win pretty easily through brute force) you can use things like OPLOCKs to give 100% reliability. 4) The mount will complete writing a new C: symbolic link to the device map. 5) Set the \GLOBAL?? directory as the new process device map directory. 6) Unmount the volume, this calls IoDeleteSymbolicLink with \DosDevices\C: which actually ends up deleting \GLOBAL??\C: 7) Remount the volume as the C: drive again (you’ll obviously need to not use C: when referring to the volume location). The user now has complete control over the contents of C:. Fixing the Issue: While technically IsDriveLetterAvailable is at fault I don’t believe fixing it would completely remove the issue. However changing IsDriveLetterAvailable to only return FALSE if STATUS_OBJECT_NAME_NOT_FOUND is returned from the ZwOpenSymbolicLink object would make it a lot harder to bypass the check. Also I don’t know if specifying the use of the mount volume driver would affect this. The correct fix would be to decide where the symbolic link is supposed to be written to and specify it explicitly. As in if you want to ensure it gets written to the current user’s drive mapping then specify the per-user directory at \Sessions\0\DosDevices\X-Y where X-Y is the authentication ID got from the SeQueryAuthenticationIdToken API. Or if it’s supposed to be in the global drive names then specify \GLOBAL??. Note this probably won’t work on pre-fast user switching versions of XP or Windows 2000 (assuming you’re still willing to support those platforms). Also I’d recommend if going the per-user route then only use the primary token (using PsReferencePrimaryToken) to determine the authentication ID as that avoids any mistakes with impersonation tokens. There’s no reason to believe that this would cause compat issues as I wouldn’t expect the normal user tool to use impersonation to map the drive for another user. Note this wasn’t reported in the iSec Partners security review so it’s not an missed fix. Proof of Concept: I’ve provided a PoC, you’ll need to build it with VS2015. It will change an arbitrary global drive letter to a VeraCrypt volume. Note it only works on VeraCrypt but it might be possible to trivially change to work on any other truecrypt derived products. You MUST build an executable to match the OS bitness otherwise it will not work. To test the PoC use the following steps. 1. Create a veracrypt volume using the normal GUI, the PoC doesn’t do this for you. Don’t mount the volume. 2. Execute the PoC, passing the drive letter you want to replace, the path to the volume file and the password for the file. e.g. MountVeracryptVolume C: c:\path\to\volume.hc password. 3. If all worked as expected eventually the PoC should print Done. At this point the drive letter you specified has been replaced with the truecrypt volume. As long as you have a command prompt open you should be able to see that the C: drive is now pointing at the encrypted volume. You can hit enter to exit the program and unmount the volume, however if you’ve replaced the system drive such as C: this will likely cause the OS to become unusable pretty quickly. Expected Result: It shouldn’t be possible to mount the volume over a global drive. Observed Result: The global drive specified has been replaced with a link to the encrypted volume. Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/38403.zip