Title: XnView Buffer Overflow Vulnerability
Advisory ID: CORE-2013-0705
Advisory URL: <http://www.coresecurity.com/advisories/xnview-buffer-overflow-vulnerability>
Date published: 2013-07-22
Date of last update: 2013-07-22
Vendors contacted: XnView
Release mode: Coordinated release
XnView ,  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.
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.
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 ®¯³µµ¶»¼½½¾¿ÁÃÇË
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