Research Archives > Security Advisories > AD20051104

Macromedia Flash Player Improper Memory Access Vulnerability

Release Date:
11/4/2005 12:00:00 AM

Date Reported:
6/27/2005 12:00:00 AM

Severity:
High

Vendor:
Macromedia

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

Overview:
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.

Protection:
Retina Network Security Scanner has been updated to identify this vulnerability.
Blink - Endpoint Vulnerability Prevention - preemptively protects from this vulnerability.

Vendor Status:
Macromedia has addressed this issue in the following security bulletin; http://www.macromedia.com/devnet/security/security_zone/mpsb05-07.html

Credit:
Discovery: Fang Xing

Greetings:
Thanks Derek and and all of the eEye guys who helped me write this advisory. Greeting xfocus guys and venustech lab guys.

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