CORE-2013-0828 - PDFCool Studio Buffer Overflow Vulnerability Oct 01 2013 04:33PM
CORE Advisories Team (advisories coresecurity com)
Core Security - Corelabs Advisory

PDFCool Studio Buffer Overflow Vulnerability

1. *Advisory Information*

Title: PDFCool Studio Buffer Overflow Vulnerability
Advisory ID: CORE-2013-0828
Advisory URL:
Date published: 2013-10-02
Date of last update: 2013-10-02
Vendors contacted: IconCool Software
Release mode: User release

2. *Vulnerability Information*

Class: Buffer overflow [CWE-119]
Impact: Code execution
Remotely Exploitable: No
Locally Exploitable: Yes
CVE Name: CVE-2013-4986

3. *Vulnerability Description*

PDFCool Studio Suite [1], [2] is prone to a security vulnerability when
processing PDF files. This vulnerability could be exploited by a remote
attacker to execute arbitrary code on the target machine by enticing
users to open a specially crafted PDF file (client-side attack).

4. *Vulnerable Packages*

. PDFAX0722_IconCool.dll v7.22.1125.2121.
. Other versions are probably affected too, but they were not checked.

5. *Vendor Information, Solutions and Workarounds*

There was no official answer from vendor after several attempts to
report this vulnerability (see [Sec. 8]). As mitigation action, given
that this is a client-side vulnerability, avoid to open untrusted PDF
files. Contact vendor for further information.

6. *Credits*

This vulnerability was discovered and researched by Marcos Accossatto
from CORE Exploit Writers Team.

7. *Technical Description / Proof of Concept Code*

Below is shown the result of opening the maliciously crafted PDF file
[3] on Windows XP SP3 (EN):

$+A50C6 > C740 14 1E000000 MOV DWORD PTR DS:[EAX+14],1E
; <== Exception - Tries to write to 909090A4
$+A50CD > 8B5424 04 MOV EDX,DWORD PTR SS:[ESP+4]
$+A50D1 > 8950 18 MOV DWORD PTR DS:[EAX+18],EDX
$+A50D4 > 8BC7 MOV EAX,EDI


At that time, the 'EAX' register contains the first 'DWORD' of our

EAX 90909090
ECX 000007B4
EDX 0012E190
EBX 048757D1
EBP 0012E064
ESI 000002F0
EDI 0012DF88
EIP 044760C6 PDFAX0~1.044760C6
C 0 ES 0023 32bit 0(FFFFFFFF)
P 1 CS 001B 32bit 0(FFFFFFFF)
A 0 SS 0023 32bit 0(FFFFFFFF)
Z 0 DS 0023 32bit 0(FFFFFFFF)
S 0 FS 003B 32bit 7FFDF000(FFF)
T 0 GS 0000 NULL
D 0
O 0 LastErr ERROR_NOT_ENOUGH_MEMORY (00000008)
EFL 00010206 (NO,NB,NE,A,NS,PE,GE,G)
ST0 empty 0.0
ST1 empty 0.0
ST2 empty 0.5000000000000000000
ST3 empty -2.9802320611338473100e-08
ST4 empty 1.0000000000000000000
ST5 empty 4.3980465111040000000e+12
ST6 empty 5.3123247893381160000e+15
ST7 empty 5.0609752291423027300e+17
3 2 1 0 E S P U O Z D I
FST 0020 Cond 0 0 0 0 Err 0 0 1 0 0 0 0 0 (GT)
FCW 137F Prec NEAR,64 Mask 1 1 1 1 1 1

The stack's exception handler is overwritten with:

0012DE00 0000000A
.... ....
0012DF6C 0EDDE2F1
0012DF70 909006EB Pointer to next SEH record
0012DF74 005D88EF SE handler

In the address '005D88EF' (the main executable module of PDFCool Studio)
we have:

005D88F0 59 POP ECX
005D88F1 C3 RETN

and the stack:

0012DA2C 7C9032A8 RETURN to ntdll.7C9032A8
0012DA30 0012DB14
0012DA34 0012DF70

So, the 'RETN' of '005D88F1' will jump to '12DF70' (the stack) where our
shellcode is located:

0012DF70 EB 06 JMP SHORT 0012DF78
0012DF72 90 NOP
0012DF73 90 NOP
0012DF74 EF OUT DX,EAX ;
I/O command
0012DF75 885D 00 MOV BYTE PTR SS:[EBP],BL
0012DF78 90 NOP

which means the normal execution flow can be altered in order to execute

arbitrary code.

8. *Report Timeline*

. 2013-09-03:
Core Security Technologies attempts to contact vendor using the IconCool
official technical support contact page [4]. No reply received.
Publication date is set for Sep 25th, 2013.

. 2013-09-09:
Core attempts to contact vendor.

. 2013-09-16:
Core attempts to contact vendor.

. 2013-09-25:
First release date missed.

. 2013-10-02:
Advisory CORE-2013-0828 published.

9. *References*

[1] http://www.iconcool.com/index.html.
[2] http://www.iconcool.com/instpdfcoolstudio.exe.

[4] IconCool technical support page http://www.iconcool.com/support.htm.

10. *About CoreLabs*

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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
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CoreLabs regularly publishes security advisories, technical papers,
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11. *About Core Security Technologies*

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and demonstrate real-world exposures to their most critical assets. Our
customers can gain real visibility into their security standing, real
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Consulting Services, CoreLabs and Engineering groups. Core Security
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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

Version: GnuPG v2.0.17 (MingW32)
Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/


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