Aloaha PDF Suite Buffer Overflow Vulnerability

Advisory ID Internal

1. Advisory Information

Title: Aloaha PDF Suite Buffer Overflow Vulnerability
Advisory ID: CORE-2013-0805
Advisory URL:
Date published: 2013-08-28
Date of last update: 2013-08-28
Vendors contacted: Aloaha Software
Release mode: User release

2. Vulnerability Information

Class: Buffer overflow [CWE-119]
Impact: Code execution
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2013-4978

3. Vulnerability Description

Aloaha PDF Suite 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 Aloaha users to open a specially crafted PDF file.

4. Vulnerable Packages

  • AloahaPDFViewer v5.0.0.7.
  • Older versions are probably affected too, but they were not checked.

5. Vendor Information, Solutions and Workarounds

There was no official answer from Aloaha 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]:

$+B6BB8 >|> 8B07 |MOV EAX,DWORD PTR DS:[EDI] $+B6BBA >|. C740 14 1E000000 |MOV DWORD PTR DS:[EAX+14],1E ; < Exception - Tries to write to 909090A4 $+B6BC1 >|. 8B5424 04 |MOV EDX,DWORD PTR SS:[ESP+4] $+B6BC5 >|. 8950 18 |MOV DWORD PTR DS:[EAX+18],EDX $+B6BC8 >|. 8BC7 |MOV EAX,EDI $+B6BCA >|. 8B10 |MOV EDX,DWORD PTR DS:[EAX] 

At that time, the registers EDX, EBX, EBP and EDI points to the shellcode; the EAX register contains the first DWORD of our shellcode:

EAX 90909090 ECX 000007B4 EDX 0012DD44 ASCII "DDDDDDDDDDDDDD..." EBX 051ACFF1 ASCII "DDDDDDDDDDDDDD..." ESP 0012D9EC EBP 0012DC54 ASCII "DDDDDDDDDDDDDD..." ESI 000002F0 EDI 0012DB78 EIP 03727BBA 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 00000206 (NO,NB,NE,A,NS,PE,GE,G) ST0 empty 16312.144994243513790 ST1 empty 3869.8214873218676080 ST2 empty -0.0 ST3 empty -0.0 ST4 empty 1.0000000000000000000 ST5 empty 4.3980465111040000000e+12 ST6 empty 5.3078580233502760000e+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 037F Prec NEAR,64 Mask 1 1 1 1 1 1 

The stack's exception handler is overwritten with:

0012D9EC FFFFF94D 0012D9F0 0000000A .... .... 0012DB5C 0EDDE2F1 0012DB60 909006EB Pointer to next SEH record 0012DB64 1106D8A0 SE handler 

In the address 1106D8A0 of AloahaTranslator.dll we have:

 1106D8A0 . 83C4 14 ADD ESP,14 1106D8A3 . C3 RETN 

and the stack:

$ ==> > 7C9032A8 RETURN to ntdll.7C9032A8 $+4 > 0012D704 $+8 > 0012DB60 $+C > 0012D720 $+10 > 0012D6D8 $+14 > 0012DB60 Pointer to next SEH record 

So, the RETN of 1106D8A3 will jump to 12DB60 (the stack) where our shellcode is located:

0012DB60 EB 06 JMP SHORT 0012DB68 0012DB62 90 NOP 0012DB63 90 NOP 0012DB64 A0 D8061190 MOV AL,BYTE PTR DS:[901106D8] 0012DB69 90 NOP 

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

8. Report Timeline

  • 2013-08-06: Core Security Technologies notifies the Aloaha team of the vulnerability. Publication date is set for Aug 27th, 2013.
  • 2013-08-06: Vendor asks for a report with technical information.
  • 2013-08-06: Technical details and proof of concept sent to Aloaha team.
  • 2013-08-12: Core asks for a status update and notifies the advisory publication was scheduled for Aug 27th. No reply received.
  • 2013-08-20: Core attempts to contact vendor.
  • 2013-08-26: Core attempts to contact vendor.
  • 2013-08-27: Release date missed.
  • 2013-08-28: After 3 attempts to contact vendor, the advisory CORE-2013-0805 is published as 'user release'.

9. References

10. About CoreLabs

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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:

13. PGP/GPG Keys

This advisory has been signed with the GPG key of Core Security Technologies advisories team.