[VulnWatch] [EEYEB-20050627B] Macromedia Flash Player Improper Memory Access Vulnerability

From: Advisories@private
Date: Fri Nov 04 2005 - 17:30:15 PST

Macromedia Flash Player Improper Memory Access Vulnerability

Release Date:
November 4, 2005

Date Reported:
June 27, 2005



Systems Affected:
Macromedia Flash 6 (on all Windows platforms) 
Macromedia Flash 7 (on all Windows platforms)

eEye Digital Security has discovered a vulnerability in Macromedia Flash
Player versions 6 and 7 that will allow an attacker to run arbitrary
code in the context of the logged in user.  An array boundary condition
may be violated by a malicious SWF file in order to redirect execution
into attacker-supplied data.

Technical Details:
The vulnerable code exists in Flash.ocx, which embodies the code
responsible for playing back SWF files.  One function maintains a large,
256-element table of function pointers on the stack, and uses a frame
type identifier read from the SWF file as an index into the array,
without enforcing the array boundaries.  The following disassembly
depicts the affected code:

    .text:1002714F    mov     eax, [esi+0CA4h]    ; type number
    .text:10027155    mov     ecx, [esi+94h]      ; base of table
    .text:1002715B    lea     eax, [ecx+eax*8]    ; get element address
    .text:1002715E    mov     ecx, [eax]          ; 

Although the index is not validated, its value is elsewhere restricted
to be at most 0x8000, so the attacker can cause a function pointer to be
retrieved from memory up to roughly 64KB after the base of the table on
the stack.  Typically this range will include heap memory, so by
planting specific data on the heap, the attacker can very easily control
the exact value of the function pointer.  Reliable exploitation using
this technique within Internet Explorer has been demonstrated by eEye
Digital Security.

Retina Network Security Scanner has been updated to identify this
Blink - Endpoint Vulnerability Prevention - protects from this

Vendor Status:
Macromedia has addressed this issue in the following security bulletin;

This vulnerability has been assigned the CVE identifier CAN-2005-2628
and OSVDB ID 18825.

Thanks Derek and and eEye guys help me wrote this advisory. Greeting
xfocus guys and venustech lab guys.

Fang Xing

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