[CORE-2015-0007] - Schneider Vampset Stack and Heap Buffer Overflow

1. Advisory Information

Title: Schneider Vampset Stack and Heap Buffer Overflow
Advisory ID: CORE-2015-0007
Advisory URL: http://www.coresecurity.com/advisories/schneider-vampset-stack-and-heap-buffer-overflow
Date published: 2015-03-30
Date of last update: 2015-03-27
Vendors contacted: Schneider
Release mode: Coordinated release

2. Vulnerability Information

Class: Heap-based Buffer Overflow [CWE-122], Stack-based Buffer Overflow [CWE-121]
Impact: Code execution
Remotely Exploitable: No
Locally Exploitable: Yes
CVE Name: CVE-2014-8390, CVE-2014-8390

3. Vulnerability Description

User-friendly and free of charge VAMPSET software [1] has been designed for setting parameters and configuring relays and is suitable for the entire VAMP range of protection relays, VAMP 321 arc flash protection unit and measuring and monitoring units. This indispensable setting and configuration tool allows relay parameters, configurations and recorded data to be exchanged between a computer and a VAMP relay using various communication cables.

VAMPSET handles the relay settings as documents, vef-files. Settings of one physical device are considered one document. Documents can be read from the relay and transferred between similar relays. Documents can also be saved to the computer hard drive, and later loaded back to the relay using VAMPSET.

VAMPSET is vulnerable to a Stack-based and Heap-based buffer overflow attack, which can be exploited by attackers to execute arbitrary code, by providing a malicious CFG or DAT file with specific parameters.

4. Vulnerable packages

VAMPSET v2.2.145

Other versions are probably affected too, but they were not checked.

5. Vendor Information, Solutions and Workarounds

Given that this is a client-side vulnerability, affected users should avoid opening untrusted .cfg or .dat files. Core Security also recommends those affected use third party software such as Sentinel [3] or EMET [2] that could help to prevent the exploitation of affected systems to some extent.

The vendor published the following advisory [5] that includes mitigation instrucctions and a reference to the updated software.

6. Credits

This vulnerability was discovered and researched by Ricardo Narvaja from Core Security Exploit Writing Team. The publication of this advisory was coordinated by Joaquin Rodriguez Varela from Core Security Advisories Team.

7. Technical Description / Proof of Concept Code

[CVE-2014-8390] This vulnerability is caused by a controlled heap buffer overflow when opening specially crafted Comtrade [4] format files.

The problem lays in the following facts. First the software allocs a fixed size in here:

.text:00494125 push 1A68h ; size_t
.text:0049412A call sub_4CC928
Then it goes to a malloc with 1A68h size:

.text:004CC92E loc_4CC92E: ; size_t
.text:004CC92E push edi
.text:004CC92F call _mallloc
And finally here:

004B3483 |> \83C6 0F ADD ESI,0F
004B3486 |. 83E6 F0 AND ESI,FFFFFFF0
004B3489 |. 56 PUSH ESI ; /HeapSize = 1A70 (6768.)
004B348A |. 6A 00 PUSH 0 ; |Flags = 0
004B348C |. FF35 2C605700 PUSH DWORD PTR DS:[57602C] ; |hHeap = 003C0000
004B3492 |. FF15 70224F00 CALL DWORD PTR DS:[<&KERNEL32.HeapAlloc>>; \HeapAlloc
After applying the AND 0f and FFFFFFF0 the size is 0x1a70:

0012EF50 003C0000 |hHeap = 003C0000
0012EF54 00000000 |Flags = 0
0012EF58 00001A70 \HeapSize = 1A70 (6768.)

Then it writes in this section without checking the size of what is written. In the POC it ends up crashing after overflowing the heap section:

00497C03 |. F3:A5 |REP MOVS DWORD PTR ES:[EDI],DWORD PTR D>
00497C05 |. 8BC8 |MOV ECX,EAX
00497C07 |. 83E1 03 |AND ECX,3
00497C0A |. F3:A4 |REP MOVS BYTE PTR ES:[EDI],BYTE PTR DS:>

00D65F60 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65F70 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65F80 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65F90 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65FA0 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65FB0 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65FC0 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65FD0 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65FE0 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC
00D65FF0 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 CCCCCCCCCCCCCCCC

EAX 00003BC6
ECX 0000082D
EDX 00003BC5
EBX 00D64468
ESP 0012ED30
EBP 00EF8290 ASCII "ASCII CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
ESI 00EF9DA0 ASCII "CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
EDI 00D66000
EIP 00497C03 Vampset.00497C03

Nevertheless, is a controllable heap overflow, therefore if a less amount of characters is used it can provoke code execution.

[CVE-2014-8390] This vulnerability is caused by a controlled stack buffer overflow when opening specially crafted Comtrade [4] format files.

When VAMPSET opens the malformed files the following occurs. It sends a message to LB_GETTEXT with the length of the string:

0013F6FC 0048E070 /CALL to SendMessageW from Vampset.0048E06E
0013F700 00840B22 |hWnd = 840B22
0013F704 00000189 |Message = LB_GETTEXT
0013F708 00000000 |Index = 0
0013F70C 0013F760 \Buffer = 0013F760

The length of that string is bigger than the destination buffer and therefore overwrites the return address that is located after the buffer:

$ ==> >49 00 4C 00 31 00 4D 00 35 00 4D 00 35 00 4D 00 I.L.1.M.5.M.5.M.
$+10 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+20 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+30 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+40 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+50 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+60 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+70 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+80 >35 00 4D 00 35 00 4D 00 35 00 4D 00 35 00 4D 00 5.M.5.M.5.M.5.M.
$+90 >35 00 4D 00 35 00 4D 00 35 00 4D 00 CC CC CC CC 5.M.5.M.5.M.IIII
$+A0 >CC CC CC CC CC CC 38 00 35 00 38 00 31 00 61 00 IIIIII8.5.8.1.a.
$+B0 >61 00 61 00 61 00 61 00 61 00 61 00 61 00 61 00 a.a.a.a.a.a.a.a.
$+C0 >61 00 61 00 61 00 61 00 61 00 61 00 61 00 61 00 a.a.a.a.a.a.a.a.
$+D0 >61 00 00 00 a…

0048E0BE > \5F POP EDI
0048E0BF . 5E POP ESI
0048E0C0 . 5D POP EBP
0048E0C1 . 5B POP EBX
0048E0C2 . 81C4 C0000000 ADD ESP,0C0
0048E0C8 . C3 RETN

From there it jumps to execution, in this case is deviated to 0x4d0035:

0013F7E0 004D0035 Vampset.004D0035
0013F7E4 004D0035 Vampset.004D0035
0013F7E8 004D0035 Vampset.004D0035
0013F7EC 004D0035 Vampset.004D0035
0013F7F0 004D0035 Vampset.004D0035
0013F7F4 004D0035 Vampset.004D0035
0013F7F8 004D0035 Vampset.004D0035

004D0035 |. FFD5 CALL EBP ; \ClientToScreen

After this it executes our code in the stack:

0013F7EC 35 004D0035 XOR EAX,35004D00
0013F7F1 004D 00 ADD BYTE PTR SS:[EBP],CL
0013F7F4 35 004D0035 XOR EAX,35004D00
0013F7F9 004D 00 ADD BYTE PTR SS:[EBP],CL
0013F7FC CC INT3
0013F7FD CC INT3
0013F7FE CC INT3
0013F7FF CC INT3
0013F800 CC INT3
0013F801 CC INT3
0013F802 CC INT3
0013F803 CC INT3
0013F804 CC INT3
0013F805 CC INT3
0013F806 3800 CMP BYTE PTR DS:[EAX],AL
0013F808 35 00380031 XOR EAX,31003800
0013F80D 0061 00 ADD BYTE PTR DS:[ECX],AH
0013F810 61 POPAD

8. Report Timeline

2015-01-29: Core Security sent an initial notification to [email protected] informing them of the vulnerability and requesting their PGP key in on order to send them the encrypted advisory draft.
2015-02-05: Core Security sent another email to [email protected] and [email protected] informing them of the vulnerability and requesting their PGP key in on order to send them the encrypted advisory draft.
2015-02-16: Schneider replied our email attaching their public PGP key, and asking if we were coordinating with ICS-CERT and the versions of their product we tested.
2015-02-20: Core Security sendt a draft copy of the Advisory. Considering that both vulnerabilities are client side and affect a software and not a device we don't think it would be necessary to contact ICS-CERT. We inform them that we are planning to release this advisory on the 20th of March, 2015.
2015-02-23: Schneider confirms the reception of Core Security draft advisory. They inform they are evaluating the report.
2015-02-27: Schneider informs they are evaluating the heap buffer overflow vulnerability and they request the Proof Of Concept files (Comtrade) we used to trigger the crash and the exploit as well. They request we coordinate a release date depending on their patch plan.
2015-03-02: Core Security sends Schneider both PoC files and explains that is our policy never to release exploit code, just the files/code that triggers the vulnerability and causes the application to crash. We also expressed our willingness to work together.
2015-03-03: Schneider confirms reception of our email and attached files.
2015-03-20: Schneider informed us that they have addressed the vulnerability and they requested that we review their security disclosure.
2015-03-25: Core Security informed Schneider that they should review the "Vulnerability Overview" section of their disclosure in order to clarify that the vulnerability could not only cause a crash in the application. We requested the time and date they are planning to publish the advisory and the update as well as the link to their publication. We informed them the URL were our advisory is going to be published and the CVE ID we are planning to use.
2015-03-25: Schneider informed us that they made the recommended modifications to their disclosure document and they sent us the new version. They also said they will publish it on their website.
2015-03-26: Core Security asked Schneider if they could inform us the exact date they are planning to publish their disclosure document. Additionally we recommended them to delay the release until Monday in order to give the affected users enough time to patch their software before the weekend.
2015-03-26: Schneider informed us that they published the advisory. They claim that because of its location, the document is not easy to find until they publicize it through a news item. They informed us that they will try to post the news item on Monday but they give no guarantees. They inform as well that they have contacted ICS-CERT so they are aware.
2015-03-27: Core Security replied Schneider that by publishing the advisory they missed the hole point of a coordinated release, even if their advisory is not easy to find online. We informed them that we are going to publish our advisory on Monday 30th at 9 am EST in order to give the affected users enough time to patch their software before the weekend.
2015-03-30: Advisory CORE-2015-0007 published.

9. References

[1] http://www.schneider-electric.com/products/ww/en/2300-ied-user-software/2320-vamp-user-software/62050-vamp-software/.
[2] http://support.microsoft.com/kb/2458544.
[3] https://github.com/CoreSecurity/sentinel.
[4] http://en.wikipedia.org/wiki/Comtrade.
[5] http://download.schneider-electric.com/files?p_Reference=SEVD-2015-084-01&amp;p_EnDocType=Brochure&amp;p_File_Id=766875737&amp;p_File_Name=SEVD-2015-084-01+VAMPSET+Software.pdf.

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12. Disclaimer

The contents of this advisory are copyright (c) 2015 Core Security and (c) 2015 CoreLabs, and are licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 (United States) License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/

13. PGP/GPG Keys

This advisory has been signed with the GPG key of Core Security advisories team, which is available for download at http://www.coresecurity.com/files/attachments/core_security_advisories.asc.