CVE-2017-16780 : Detail

CVE-2017-16780

9.8
/
Critical
Cross-Site Request Forgery - CSRF
A01-Broken Access Control
1.99%V3
Network
2017-11-10
22h00 +00:00
2017-11-20
09h57 +00:00
CVE.org
NVD
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CVE Descriptions

The installer in MyBB before 1.8.13 allows remote attackers to execute arbitrary code by writing to the configuration file.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-352 Cross-Site Request Forgery (CSRF)
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.

Metrics

Metrics Score Severity CVSS Vector Source
V3.0 9.8 CRITICAL CVSS:3.0/AV:N/AC:L/PR:N/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.

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.

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.

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.

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 7.5 AV:N/AC:L/Au:N/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 : 43136

Publication date : 2017-11-10 23h00 +00:00
Author : Pabstersac
EDB Verified : Yes

# Exploit Title: RCE in MyBB up to 1.8.13 via installer # Date: Found on 05-29-2017 # Exploit Author: Pablo Sacristan # Vendor Homepage: https://mybb.com/ # Version: Version > 1.8.13 (Fixed in 1.8.13) # CVE : CVE-2017-16780 This RCE can be executed via CSRF but doesn't require it (in some special cases). The requirements are there shouldn't be a lock in the /install/ directory and then if you have access to the install directory you don't need CSRF, but if you don't then you need CSRF. I have included a patch and a description. The exploit will write PHP code to /inc/config.php which is then 'REQUIRE'd in most of the pages in MyBB, the PoC will just write lollol to the top of every page in MyBB. I also have an XSS but that I will report later. There is a CSRF vulnerability in MyBB /install/index.php which can be used to inject PHP code into /inc/config.php which is then used in most of the pages (require MYBB_ROOT."/inc/config.php" is in most of the pages). The vulnerability exists in the table creation process for sqlite databases, this is because the Database Path is then inserted into the /inc/config.php file in line 11 as $config['database']['database'] = 'DB Path'; The vulnerability occurs because MyBB doesn't properly escape the Database Path, allowing an attacker to easily inject PHP by inserting a DB Path of : lol'; echo 'lol this will not cause any parse errors since there will be a : '; added at the end. Of course the attacker can easily just execute code in the server, getting backdoor access to the server easily. A PoC would be to host a site like this: <form name="x" action="http://localhost/install/index.php" method="post"> <input type="hidden" name='dbengine' value="sqlite"> <input type="hidden" name='config[sqlite][dbname]' value="lol'; echo 'lol"> <input type="hidden" name='config[sqlite][tableprefix]' value="mybb_"> <input type="hidden" name='action' value="create_tables"> </form> <script>document.x.submit();</script> And when a victim logged in as admin to a MyBB website visits this site they will have a "lollol" at the top of every page (or you can also make it do much more malicious things). A simple patch would be to change /install/index.php:1410 to: if(strstr($config['dbname'], "./") !== false || strstr($config['dbname'], "../") !== false || strstr($config['dbname'], "'") !== false || empty($config['dbname']))

Products Mentioned

Configuraton 0

Mybb>>Mybb >> Version To (including) 1.8.12

References

https://www.exploit-db.com/exploits/43136/
Tags : exploit, x_refsource_EXPLOIT-DB