CVE-2019-1019 : Detail

CVE-2019-1019

8.5
/
High
A01-Broken Access Control
0.93%V3
Network
2019-06-12
11h49 +00:00
2019-07-15
14h06 +00:00
CVE.org
NVD
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CVE Descriptions

A security feature bypass vulnerability exists where a NETLOGON message is able to obtain the session key and sign messages.To exploit this vulnerability, an attacker could send a specially crafted authentication request, aka 'Microsoft Windows Security Feature Bypass Vulnerability'.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

Metrics

Metrics Score Severity CVSS Vector Source
V3.0 8.5 HIGH CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/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.

Network

A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers).

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.

Changed

An exploited vulnerability can affect resources beyond the authorization privileges intended by the vulnerable component. In this case the vulnerable component and the impacted component are different.

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 6 AV:N/AC:M/Au:S/C:P/I:P/A:P [email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 47115

Publication date : 2019-07-11 22h00 +00:00
Author : Google Security Research
EDB Verified : Yes

VULNERABILITY DETAILS It's possible to use the NTLM reflection attack to escape a browser sandbox in the case where the sandboxed process is allowed to create TCP sockets. In particular, I was able to combine the issues mentioned below with a bug in Chromium to escape its sandbox. ## HTTP -> SMB NTLM reflection This is a long known attack that was described, for example, in https://bugs.chromium.org/p/project-zero/issues/detail?id=222. As far as I can tell, MS16-075 was supposed to to fix it by blocking attempts to reflect NTLM authentication operating in the same machine mode (not sure about the actual internal term for that). However, it's still possible to reflect NTLM authentication that works in the regular remote mode, and an attacker can force the parties to use the remote mode, for example, by clearing the NTLMSSP_NEGOTIATE_OEM_DOMAIN_SUPPLIED flag in the initial NEGOTIATE_MESSAGE message. In the actual exploit, a compromised sandboxed process acts as both a web server and an SMB client, and asks the browser to visit http://localhost:[fake_webserver_port]. The browser receives an NTLM authentication request and considers the `localhost` domain to be safe to automatically log on with the current user's credentials. The sandboxed process forwards the corresponding packets to the local SMB server. The problem here is that since the established session is considered remotely authenticated, it's not allowed to access administrative shares unless the browser process runs at the high integrity level. Therefore, another bug is required to gain file system access. ## Insufficient path check in EFSRPC The Encrypting File System Remote Protocol is a Remote Procedure Call interface that is used to manage data objects stored in an encrypted form. It supports backing up and restoring files over SMB, among other things. Functions like `EfsRpcOpenFileRaw` implement security checks, i.e., they forbid remote users to pass regular file paths. However, if the attacker passes a UNC path of the form `\\localhost\C$\...`, `lsass.exe` will initiate a new SMB connection while impersonating the calling user, but this time using the same machine mode authentication; therefore it will be permitted to access the C$ share. The exploit saves the payload on the user's disk (the easiest way might be just to force it to be auto-downloaded as a .txt file) and calls the EFSRPC methods to copy it as an .exe file to the user's Startup folder. There's also another path check bypass that has been found by James Forshaw. `EfsRpcOpenFileRaw` accepts file paths starting with `\\.\C:\...`, presumably thinking that it's a UNC path since it starts with two back-slashes. Please note that this variant also works in the case where a regular user's credentials are relayed to another machine in a domain, so it might have wider security implications. It's also worth mentioning that the `efsrpc` named pipe might not be enabled by default, but the same RPC endpoint is available on the `lsass` named pipe with UUID [c681d488-d850-11d0-8c52-00c04fd90f7e]. REPRODUCTION CASE The proof-of-concept is based on [impacket](https://github.com/SecureAuthCorp/impacket/). It's a collection of Python classes that supports working with SMB and MSRPC. 1. Run `start.cmd`, which downloads impacket from Github, applies the patch, and starts the server. 2. Open http://localhost/ in a Chromium-based browser. 3. You should see a new .exe file appearing on your desktop. VERSION Microsoft Windows [Version 10.0.17134.648] REFERENCES https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-nlmp/b38c36ed-2804-4868-a9ff-8dd3182128e4 https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-efsr/08796ba8-01c8-4872-9221-1000ec2eff31 Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/47115.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_10 >> Version 1903

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 1803

Microsoft>>Windows_server_2016 >> Version 1903

Microsoft>>Windows_server_2019 >> Version -

References