podofo: NULL pointer dereference in ColorChanger::GetColorFromStack (colorchanger.cpp)

Description:
podofo is a C++ library to work with the PDF file format.

A fuzz on it discovered a null pointer access. The upstream project denies me to open a new ticket. So, I just will forward this on the -users mailing list.

The complete ASan output:

# podofocolor dummy $FILE foo
==18954==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x00000052302d bp 0x7fc24b8e2000 sp 0x7ffcaaf21810 T0)
==18954==The signal is caused by a READ memory access.
==18954==Hint: address points to the zero page.
    #0 0x52302c in getVtablePrefix /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cc:198
    #1 0x52302c in __ubsan::checkDynamicType(void*, void*, unsigned long) /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cc:221
    #2 0x521082 in HandleDynamicTypeCacheMiss /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/ubsan/ubsan_handlers_cxx.cc:37
    #3 0x521922 in __ubsan_handle_dynamic_type_cache_miss /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/ubsan/ubsan_handlers_cxx.cc:87
    #4 0x538eb2 in ColorChanger::GetColorFromStack(int, std::vector<PoDoFo::PdfVariant, std::allocator >&) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/colorchanger.cpp:430:33
    #5 0x530d50 in ColorChanger::ProcessColor(ColorChanger::EKeywordType, int, std::vector<PoDoFo::PdfVariant, std::allocator >&, GraphicsStack&) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/colorchanger.cpp:449:28
    #6 0x52c2a9 in ColorChanger::ReplaceColorsInPage(PoDoFo::PdfCanvas*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/colorchanger.cpp:214:31
    #7 0x526921 in ColorChanger::start() /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/colorchanger.cpp:120:15
    #8 0x523b8d in main /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/podofocolor.cpp:116:12
    #9 0x7fc2490df78f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #10 0x4300e8 in _start (/usr/bin/podofocolor+0x4300e8)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/ubsan/ubsan_type_hash_itanium.cc:198 in getVtablePrefix
==18954==ABORTING

Affected version:
0.9.5

Fixed version:
N/A

Commit fix:
N/A

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

CVE:
CVE-2017-6842

Reproducer:
https://github.com/asarubbo/poc/blob/master/00217-podofo-nullptr-colorchanger-cpp

Timeline:
2017-03-01: bug discovered
2017-03-02: bug reported upstream
2017-03-02: blog post about the issue
2017-03-12: CVE assigned

Note:
This bug was found with American Fuzzy Lop.

Permalink:

podofo: NULL pointer dereference in ColorChanger::GetColorFromStack (colorchanger.cpp)

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