Denial of service & heap-based buffer overflow

SEC Consult Vulnerability Lab Security Advisory < 20161128-0 >


title: Denial of service & heap-based buffer overflow

product: Guidance Software EnCase Forensic Imager & EnCase Forensic

vulnerable version: EnCase Forensic Imager<= 7.10

EnCase Forensic (tested with version

fixed version: -

CVE number: -

impact: high


found: 2016-09-30

by: Wolfgang Ettlinger (Office Vienna)

SEC Consult Vulnerability Lab

An integrated part of SEC Consult

Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow

Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich


Vendor description:


"When time is short and you need to acquire entire volumes or selected

individual folders, EnCase Forensic Imager is your tool of choice. Based on

trusted, industry-standard EnCase Forensic technology, EnCase Forensic Imager:

* Is free to download and use

* Requires no installation

* Is a standalone product that does not require an EnCase Forensic license

* Enables acquisition of local drives (network drives are not able to be

acquired with Imager)

* Provides easy viewing and browsing of potential evidence files, including

folder structures and file metadata

* Can be deployed via USB stick and used to perform acquisition of a live




Business recommendation:


SEC Consult recommends not to use Encase Forensic Imager or the Encase Forensic

Suite until a thorough security review has been performed by security

professionals and all identified issues have been resolved.


Vulnerability overview/description:


1) Denial of Service

Several manipulated hard disk images cause Encase Forensic Imager to crash. A

suspect manipulating the hard drive could potentially hinder an investigator

from using Encase Forensic Imager for creating hard disk images.

Encase Forensic (v7) has been tested and found to be affected as well.

2) Heap-based buffer overflow

Using a manipulated ReiserFS image an attacker can overwrite heap memory on the

investigator's machine. Because of several restrictions SEC Consult was unable

to create an exploit that works reliably within a reasonable timeframe.

However, as with most heap-based buffer overflow vulnerabilities it is possible

that an attacker could gain arbitrary code execution nevertheless.


Proof of concept:


SEC Consult has created proof of concept disk images that will crash Encase. Those

PoC images will not be released.

1) Denial of Service

The following list demonstrates cases that cause Encase to crash. The

investigators would be unable to analyze the hard disk/partition/image using the

affected products:

* Ext3:

- Several conditions cause Encase Forensic Imager to encounter an div/0

exception. Disk images that were manipulated in the following way

demonstrate this issue. Those crashes have not been further

investigated as to whether code execution is possible.

+ nummer of blocks per group: 0xFFFFFFFF

+ total numer of blocks: 0xFFFFFFFF

+ last mount path: 'A'*100000

+ volume name: 'A'*100000

+ block number of the superblock: 0

+ FS-Id: 'A'*100000

- Manipulating the size of the inode structure value (e.g. 0xFFFF) causes

Encase Forensic Imager to write beyond the limits of a previously

allocated (VirtualAlloc) segment.

* Iso9660:

- If the length of a file name is specified in a way that it would exceed

the end of the last block, Encase Forensic Imager crashes while trying to

read beyond an allocated segment.

* ReiserFs:

- When setting a block size of below 0x200 the application overwrites heap

memory with attacker-supplied data.

* GPT:

- When specifying an overly long name (in our setup longer than 0x3fc6) for a

partition, Encase Forensic crashes failing to read memory when trying to

determine the length of the string. The partition table can be constructed

in a way that it can also be used for storing data. However, an investigator

using Encase will not be able to analyze it.

2) Heap-based buffer overflow

The manipulated ReiserFs image that causes the application to overwrite heap

memory can be tuned to overwrite heap-data with attacker-controlled data.

The application calculates a value (here called "dev_block_count") as:

dev_block_count =

blocksize from image (e.g. 0x200)

/ blocksize of reading device (typically 0x200)

* number of blocks

.text:006F5306 mov ecx, [esi+14Ch] ; ecx = blocksize (device, 0x200)

.text:006F530C movzx eax, [esp+90h+var_54] ; eax = blocksize (img)

.text:006F5311 xor edx, edx

.text:006F5313 div ecx ; div eax / ecx

.text:006F5315 push 0

.text:006F5317 mov edx, eax

.text:006F5319 imul edx, [esp+94h+var_80] ; * numblocks

If this value is zero (which is the case when the blocksize from the image is

smaller than 0x200), later in the program it is corrected to the value 1


This causes the application to later allocate 4 bytes of memory (the corrected

value of 1 * 4, @006F5426).

Then the first block of the image is copied to the allocated 4-byte heap space.

The length to be copied is calculated based on the number of blocks specified

in the image (maximum 0x200).


Vulnerable / tested versions:


At least version 7.10 of Encase Forensic Imager has been found to be vulnerable.

This version was the latest at the time the security vulnerabilities were


The disk images that caused crashes for Encase Forensic Imager also caused

crashes with Encase Forensic version It is unknown whether

Encase Forensic v8 is affected as well.


Vendor contact timeline:


2016-10-07: Contacting vendor (sales team) through email, requesting security

contact, sending responsible disclosure policy & encryption keys

2016-10-14: No answer, extending email recipient list, requesting security

contact again

2016-10-14: Vendor: our request has been sent to management team, they will

follow up

2016-10-17: Vendor: one of their security representatives will be reaching

out shortly.

2016-10-28: Asking again for security contact, kind reminder of latest release

date per 2016-11-26

2016-10-28: Vendor: Verified that request has been passed on to proper

department, they will follow up on this

2016-11-07: Asking again for security contact, reminding them again that

release date is in about three weeks

2016-11-08: Extending email recipient list again, including SVP Product

Engineering explaining unsuccessful attempts to receive a

security contact

2016-11-14: Still no answer, reminding Guidance Software again about the release

date which has been set to 2016-11-28 now. Told them that the

initial vulnerabilities also affect Encase Forensic and not only

Encase Forensic Imager.

2016-11-14: Vendor: "send the alleged vulnerability to us for review" (signed


2016-11-14: Sending the advisory encrypted to the vendor, including proof of

concept disk images to reproduce the issues

2016-11-14: Vendor: "We will look at the issues and will address them in future

release(s) if necessary"

2016-11-15: Asking if there is a hotfix planned, offering to delay the advisory

release for a few days if necessary, otherwise we'll keep the set

release date

2016-11-15: Vendor: they will fix the issue later and are fine patching it after

advisory release

2016-11-25: Asking if any fixes are available

2016-11-28: Releasing security advisory




The vendor told SEC Consult they investigate the issues and will fix them at a

later date.






Advisory URL:




SEC Consult Vulnerability Lab

SEC Consult

Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow

Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich

About SEC Consult Vulnerability Lab

The SEC Consult Vulnerability Lab is an integrated part of SEC Consult. It

ensures the continued knowledge gain of SEC Consult in the field of network

and application security to stay ahead of the attacker. The SEC Consult

Vulnerability Lab supports high-quality penetration testing and the evaluation

of new offensive and defensive technologies for our customers. Hence our

customers obtain the most current information about vulnerabilities and valid

recommendation about the risk profile of new technologies.


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EOF W. Ettlinger / @2016