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Untrusted Pointer Dereference Vulnerability in Corel WordPerfect X6

Advisory ID:HTB23114
Product:Corel WordPerfect X6 Standard Edition
Vendor:Corel Corporation
Vulnerable Versions:16.0.0.388, other versions may be also affected
Tested Version:16.0.0.388 on Windows 7 SP1 32 bits
Advisory Publication:September 12, 2012 [without technical details]
Vendor Notification:September 12, 2012
Public Disclosure:March 7, 2013
Latest Update:March 7, 2013
Vulnerability Type:Untrusted Pointer Dereference [CWE-822]
CVE Reference:CVE-2012-4900
Risk Level:Low
CVSSv2 Base Score:2.6 (AV:N/AC:H/Au:N/C:N/I:N/A:P)
Discovered and Provided:High-Tech Bridge Security Research Lab
 

Advisory Details:

High-Tech Bridge Security Research Lab discovered an untrusted pointer dereference vulnerability in Corel WordPerfect. Opening of a malicious WPD (WordPerfect Document) causes immediate application crash, resulting in a loss of all unsaved current application data of the user.


1) Untrusted Pointer Dereference Vulnerability in Corel WordPerfect X6: CVE-2012-4900

The very beginning of the crash occurs within the WPWIN16.DLL module in the STARTAPP function when the application attempts to call the STRNICMP procedure in the MSVCR80 module. Due to a specially crafted WPD file and as a result of the stack modification, it is possible to partially control the destination pointer [EDI] inherited by the STRNICMP function.

Crash details:
eax=0225a848 ebx=0224ce48 ecx=00000008 edx=00000008 esi=0224ce48 edi=0225a848
eip=69fe74bc esp=0012ee80 ebp=0012ee9c iopl=0 nv up ei pl nz na po cy
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010203


MSVCR80!strnicmp+0x261:
69fe74bc f3a4 rep movs byte ptr es:[edi],byte ptr [esi]
Exception Faulting Address: 0x225a848
First Chance Exception Type: STATUS_ACCESS_VIOLATION (0xC0000005)

Exception Sub-Type: Write Access Violation


Stack Trace:
MSVCR80!strnicmp+0x261
wpwin16!StartApp+0xbdc8e
wpwin16!StartApp+0xc5ef1
wpwin16!StartApp+0xc67f3
wpwin16!StartApp+0xc0758
ntdll!RtlAllocateHeap+0x211
ntdll!RtlAllocateHeap+0xac
ntdll!RtlTryEnt erCriticalSection+0x9ba
ntdll!RtlTryEnterCriticalSection+0x98f
WStr16!WPwmemcpy+0x1e
PFIT160!wrea d+0xe1
MSVCR80!strnicmp+0x135
wpwin16!StartApp+0xdfe00


In order to exploit the vulnerability remotely the attacker has to send a malicious file to the victim by email. In a web-based scenario, the attacker can host a malicious file on a website or WebDav share and trick the victim to download and open the file.

As a PoC (Proof of Concept) a file "PoC.wpd" is provided, which causes immediate application crash. Password for archive: k2-0xj)Dhfjhlfs


Solution:
Currently we are not aware of any solutions from the Vendor.

Disclosure Timeline:
2012-09-12: Vendor Notified.
2012-09-19: Request for security fix date.
2012-09-27: Vendor says that the "vulnerabilities will be fixed with the next Service Pack".
2012-10-16: Vendor re-requested to provide a date of security fix.
2012-11-20: WordPerfect Office X6 Service Pack 2 release, vulnerability is not fixed.
2012-11-26: Vendor re-requested to provide a date of security fix.
2013-02-04: WordPerfect Office X6 Hot Patch 1 release, vulnerability is not fixed.
2013-02-26: Vendor re-requested to provide a date of security fix.
2013-03-07: Public Disclosure [Disclosure Policy].


ImmuniWeb by High-Tech Bridge


References:
[1] High-Tech Bridge Advisory HTB23114 - https://www.htbridge.com/advisory/HTB23114 - Untrusted Pointer Dereference Vulnerability in Corel WordPerfect X6.
[2] Corel Corporation - http://www.corel.com - WordPerfect is a word processing application of Corel's WordPerfect Office suite.
[3] Common Vulnerabilities and Exposures (CVE) - http://cve.mitre.org/ - international in scope and free for public use, CVE® is a dictionary of publicly known information security vulnerabilities and exposures.
[4] Common Weakness Enumeration (CWE) - http://cwe.mitre.org - targeted to developers and security practitioners, CWE is a formal list of software weakness types.

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