Core Security - Corelabs Advisory http://corelabs.coresecurity.com/ IcoFX Buffer Overflow Vulnerability 1. *Advisory Information* Title: IcoFX Buffer Overflow Vulnerability Advisory ID: CORE-2013-1107 Advisory URL: http://www.coresecurity.com/advisories/icofx-buffer-overflow-vulnerability Date published: 2013-12-10 Date of last update: 2013-12-10 Vendors contacted: IcoFX 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-2013-4988 3. *Vulnerability Description* IcoFX [1] is prone to a (client side) security vulnerability when processing .ICO files. This vulnerability could be exploited by a remote attacker to execute arbitrary code on the target machine, by enticing the user of IcoFX to open a specially crafted icon file. 4. *Vulnerable Packages* . IcoFX v2.5.0.0 for Windows. . 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 ICO files. Contact vendor for further information. 6. *Credits* This vulnerability was discovered and researched by Marcos Accossatto 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 'CORE-2013-1107-icofx-poc.ico'[2] on Windows XP SP3 (EN). The vulnerable function is located in 0x80D9F8. By loading the PoC, the loop [0x80DA74, 0x80DA93] fills the buffer and overwrite the Exception Handler: /----- 0080DA74 8B45 E8 MOV EAX,DWORD PTR SS:[EBP-18] 0080DA77 03C0 ADD EAX,EAX 0080DA79 8D94C5 8CF9FFFF LEA EDX,DWORD PTR SS:[EBP+EAX*8-674] 0080DA80 B9 10000000 MOV ECX,10 ; Will copy 16 bytes from file to buffer 0080DA85 8B45 F8 MOV EAX,DWORD PTR SS:[EBP-8] 0080DA88 8B18 MOV EBX,DWORD PTR DS:[EAX] 0080DA8A FF53 0C CALL DWORD PTR DS:[EBX+C] 0080DA8D FF45 E8 INC DWORD PTR SS:[EBP-18] ; Index, will be overwritten with our value in the penultimate loop turn 0080DA90 FF4D DC DEC DWORD PTR SS:[EBP-24] ; Counter, will be overwritten with our value in the penultimate loop turn 0080DA93 75 DF JNZ SHORT 0080DA74 0080DA95 0FBF45 F0 MOVSX EAX,WORD PTR SS:[EBP-10] -----/ At the 'MOVSX' of 0x80DA95, the CPU registers are as follows: /----- EAX 00000010 ECX 7C80189C kernel32.7C80189C EDX 00000010 EBX 004617F4 IcoFX2.004617F4 ESP 0012F380 EBP 0012FA08 ESI 005B2CBC IcoFX2.005B2CBC EDI 02555C80 EIP 0080DA95 IcoFX2.0080DA95 C 1 ES 0023 32bit 0(FFFFFFFF) P 1 CS 001B 32bit 0(FFFFFFFF) A 0 SS 0023 32bit 0(FFFFFFFF) Z 1 DS 0023 32bit 0(FFFFFFFF) S 0 FS 003B 32bit 7FFDF000(FFF) T 0 GS 0000 NULL D 0 O 0 LastErr ERROR_SUCCESS (00000000) EFL 00200247 (NO,B,E,BE,NS,PE,GE,LE) ST0 empty -??? FFFF 00F300F3 00F300F3 ST1 empty -??? FFFF 00FE00FE 00FE00FE ST2 empty -??? FFFF 00000009 00220065 ST3 empty -??? FFFF 0000000A 00240069 ST4 empty 1.2948274137727088000e+16 ST5 empty 2.5896178900861029000e+16 ST6 empty 3.2651492439228483000e+16 ST7 empty 3.1244147623526446000e+16 3 2 1 0 E S P U O Z D I FST 0000 Cond 0 0 0 0 Err 0 0 0 0 0 0 0 0 (GT) FCW 1272 Prec NEAR,53 Mask 1 1 0 0 1 0 -----/ And the stack Exception Handler is overwritten (shellcode starts in 0x12F3A4): /----- 0012F380 0012FA10 Pointer to next SEH record 0012F384 42424242 SE handler 0012F388 41414141 0012F38C 41414141 0012F390 41414141 0012F394 000502A8 0012F398 7E4188A6 USER32.GetWindowLongW 0012F39C 00000000 0012F3A0 0012F3D8 ASCII "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"... 0012F3A4 41414141 -----/ As a result, the normal execution flow can be altered in order to execute arbitrary code. 8. *Report Timeline* . 2013-11-11: Core Security Technologies attempts to contact the IcoFX team; no reply received. Publication date is set for Dec 3rd, 2013. . 2013-11-14: Core attempts to contact vendor. . 2013-11-26: Core attempts to contact vendor. . 2013-12-03: Core attempts to contact vendor. . 2013-12-03: First release date missed. . 2013-12-10: Advisory CORE-2013-1107 published. 9. *References* [1] http://icofx.ro/. [2] http://www.coresecurity.com/system/files/attachments/2013/12/CORE-2013-1107-icofx-poc.zip 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: http://corelabs.coresecurity.com. 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: http://www.coresecurity.com. 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 http://www.coresecurity.com/files/attachments/core_security_advisories.asc.