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# Title : XnView 2.03 (.PCT) - Buffer Overflow Vulnerability
# Published : 2013-07-23
# Author :
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Core Security - Corelabs Advisory

XnView Buffer Overflow Vulnerability

1. *Advisory Information*

Title: XnView Buffer Overflow Vulnerability
Advisory ID: CORE-2013-0705
Advisory URL:
Date published: 2013-07-22
Date of last update: 2013-07-22
Vendors contacted: XnView
Release mode: Coordinated release

2. *Vulnerability Information*

Class: Buffer overflow [CWE-119]
Impact: Code execution
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2013-2577

3. *Vulnerability Description*

XnView [1], [2] is prone to a security vulnerability when processing PCT
files. This vulnerability could be exploited by a remote attacker to
execute arbitrary code on the target machine, by enticing the user of
XnView to open a specially crafted file.

4. *Vulnerable Packages*

   . XnView v2.03 for Windows.
   . Older versions are probably affected too, but they were not checked.

5. *Non-Vulnerable Packages*

   . XnView v2.04.

6. *Credits*

This vulnerability was discovered and researched by Ricardo Narvaja from
Core Exploit Writers Team. The publication of this advisory was
coordinated by Fernando Miranda from Core Advisories Team.

7. *Technical Description / Proof of Concept Code*

Below is shown the result of opening the maliciously crafted file

7C9108F3    8902            MOV DWORD PTR DS:[EDX],EAX
7C9108F5    8941 04         MOV DWORD PTR DS:[ECX+4],EAX
7C9108F8    56              PUSH ESI
7C9108F9    8B75 C8         MOV ESI,DWORD PTR SS:[EBP-38]
7C9108FC    56              PUSH ESI
7C9108FD    E8 BAFDFFFF     CALL ntdll.7C9106BC         << CRASH

EAX 00EC3008
ECX 003C95B0
EDX 41424344
EBX 003C0178
ESP 0013E708
EBP 0013E7C4
ESI 00EC3000
EDI 003C0000
EIP 7C9108F3 ntdll.7C9108F3
C 1  ES 0023 32bit 0(FFFFFFFF)
P 0  CS 001B 32bit 0(FFFFFFFF)
A 1  SS 0023 32bit 0(FFFFFFFF)
Z 0  DS 0023 32bit 0(FFFFFFFF)
S 1  FS 003B 32bit 7FFDF000(FFF)
T 0  GS 0000 NULL
D 0
O 0  LastErr ERROR_NO_SCROLLBARS (000005A7)
EFL 00010293 (NO,B,NE,BE,S,PO,L,LE)
ST0 empty +UNORM 043E 7C910435 0007DC88
ST1 empty +UNORM 0002 0007DB84 00020024
ST2 empty -UNORM DA40 7C901000 7FFDE000
ST3 empty +UNORM 0460 7C90E920 0007DB14
ST4 empty +UNORM 0208 7C913F85 7C913F92
ST5 empty +UNORM 0044 77DDE250 0007DE54
ST6 empty 0.0000000000000006002
ST7 empty 0.0000000000000006002
               3 2 1 0      E S P U O Z D I
FST 4020  Cond 1 0 0 0  Err 0 0 1 0 0 0 0 0  (EQ)
FCW 027F  Prec NEAR,53  Mask    1 1 1 1 1 1

As a result, the address 0x41424344 (controlled by the attacker) can be
overwritten and the normal execution flow can be altered in order to
execute arbitrary code.

003C95B0  32 32 33 34 44 43 42 41 AA AA AA AA 34 35 36 37  2234DCBAaaaa4567
003C95C0  38 90 91 26 32 32 26 3C 36 32 36 36 32 36 3C 3C  8??&22&<626626<<
003C95D0  54 65 6D 73 82 82 87 90 90 99 9A 9B 9E A1 A6 AA  Tems??????????|a
003C95E0  AE AF B3 B5 B5 B6 BB BC BD BD BE BF C1 C3 C7 CB  ?3̦??????????

8. *Report Timeline*
. 2013-07-04:
Core Security Technologies notifies the XnView team of the
vulnerability. Publication date is set for July 31st, 2013.

. 2013-07-09:
Vendor asks for a report with technical information.

. 2013-07-10:
Technical details sent to XnView team.

. 2013-07-11:
Vendor notifies that the issue will be fixed in the next product release.

. 2013-07-15:
Core asks when the next release has been scheduled.

. 2013-07-16:
Vendor notifies that the next product release is scheduled for next week.

. 2013-07-17:
Core re-schedules the advisory publication for Monday 22nd.

. 2013-07-22:
Advisory CORE-2013-0705 released.

9. *References*

[1] http://www.xnview.com/.
[2] http://www.xnview.com/en/xnview/.

10. *About CoreLabs*

CoreLabs, the research center of Core Security Technologies, is charged
with anticipating the future needs and requirements for information
security technologies. We conduct our research in several important
areas of computer security including system vulnerabilities, cyber
attack planning and simulation, source code auditing, and cryptography.
Our results include problem formalization, identification of
vulnerabilities, novel solutions and prototypes for new technologies.
CoreLabs regularly publishes security advisories, technical papers,
project information and shared software tools for public use at:

11. *About Core Security Technologies*

Core Security Technologies enables organizations to get ahead of threats
with security test and measurement solutions that continuously identify
and demonstrate real-world exposures to their most critical assets. Our
customers can gain real visibility into their security standing, real
validation of their security controls, and real metrics to more
effectively secure their organizations.

Core Security's software solutions build on over a decade of trusted
research and leading-edge threat expertise from the company's Security
Consulting Services, CoreLabs and Engineering groups. Core Security
Technologies can be reached at +1 (617) 399-6980 or on the Web at:

12. *Disclaimer*

The contents of this advisory are copyright (c) 2013 Core Security
Technologies and (c) 2013 CoreLabs, and are licensed under a Creative
Commons Attribution Non-Commercial Share-Alike 3.0 (United States)
License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/

13. *PGP/GPG Keys*

This advisory has been signed with the GPG key of Core Security
Technologies advisories team, which is available for download at