FL Studio 5 (.flp file processing) Heap Overflow

Release Date:--
26th September 2005

Severity:--
High (Arbitrary Code Execution)

Vendor:--
Image-Line Software

Vendor Status:--
Vendor Contacted --- No Response

Systems Affected:--
Fl Studio v5.0.1 (Confirmed)
Vulnerability may also exist in previous and current versions

Background:-- 
FL Studio is a full-featured sequencer perfectly suited for creation of complex songs and realistic drum loops, with 32 bit internal mixing and advanced MIDI support.

Vulnerability Details:-- 
The FL Studio component in FLEngine.dll, that processes .flp files, is susceptible to a Heap overflow Vulnerability. ?.flp? files are equivalent to project files and are used to store information related to song composition.

This is a text book Heap overflow scenario and is trivially exploitable. The adversary can manipulate two registers by using overflowed data and thereby control the pointer exchange taking place when heap management routine kicks in. To exploit this he would have to create a ?.flp? file containing the trigger and malicious payload.

Since this is a closed File format, the vulnerable structure cannot be pin pointed precisely. However the vulnerability definitely exists in code that processes file paths. FL Studio allows inclusion of various .mid or .wav files for use a samples. When a session is saved, the path to these samples is also saved in the .flp file. Manipulating these path names to contain 128 bytes or more triggers the Heap Overflow.

The vulnerability gets triggered once the user closes the malicious .flp file. This makes it even more deceiving since the application does not crash or exhibit suspicious behavior when the file is opened.

This issue has been tested and confirmed in FL Studio v5.0.1 on Windows XP SP1. The latest version is FL Studio v5.0.2b. It is highly possible that previous and current versions are also vulnerable.

Attack Vectors and Impact:-- 
In order to exploit this vulnerability an attacker can craft a malicious .flp file containing executable payload and transmit it to a FL studio user over mail or chat. User interaction would be required for opening the file.

Apart from this FL studio has massive online communities and lists. A malicious .flp file can also be posted in one of these forums to execute a large scale compromise.

Exploitation of this vulnerability will allow arbitrary code execution with privileges of the user who opened the file.

PoC/Exploit Code:--

Editing any file bundled along with the package would demonstrate the vulnerability. Manipulate data in ?Getting Started.flp? at the following offsets:-

00001480  C4 21 5C 50 61 74 63 68 65 73 5C 50 61 63 6B 73    Ä!PatchesPacks
00001490  5C 44 61 6E 63 65 5C 44 4E 43 5F 48 61 74 2E 77    DanceDNC_Hat.w
000014A0  61 76 00 C0 08 44 4E 43 5F 48 61 74 00 80 83 83    av.?.DNC_Hat.???
000014B0  83 00 41 01 00 48 01 2A 5B 01 01 5B 02 01 48 05    ?.A..H.*[..[..H.
000014C0  2A 5B 05 01 5B 06 01 48 09 2A 5B 09 01 5B 0A 01    *[..[..H.*[..[..
000014D0  48 0D 2A 5B 0D 01 5B 0E 01 98 00 00 00 00 E9 41    H.*[..[..?....éA
000014E0  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
000014F0  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
00001500  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
00001510  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
00001520  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
00001530  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
00001540  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41    AAAAAAAAAAAAAAAA
00001550  41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 03    AAAAAAAAAAAAAAA.

Opening this file in FL Studio with a debugger attached would illustrate the user controlled pointer exchange taking place.

Workaround: 
Currently not aware of any work around

Greetz: Jhaangi, Gunnu

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