podofo: NULL pointer dereference in GraphicsStack::TGraphicsStackElement::~TGraphicsStackElement (graphicsstack.h)

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

A fuzz on it discovered a null pointer dereference. 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
==7677==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x00000054b701 bp 0x7ffe64ec7cb0 sp 0x7ffe64ec7c80 T0)
==7677==The signal is caused by a READ memory access.
==7677==Hint: address points to the zero page.
    #0 0x54b700 in GraphicsStack::TGraphicsStackElement::~TGraphicsStackElement() /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/graphicsstack.h:29:11
    #1 0x55b772 in std::deque<GraphicsStack::TGraphicsStackElement, std::allocator >::pop_back() /usr/lib/gcc/x86_64-pc-linux-gnu/4.9.4/include/g++-v4/bits/stl_deque.h:1459:4
    #2 0x52c84d in ColorChanger::ReplaceColorsInPage(PoDoFo::PdfCanvas*) /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/colorchanger.cpp:190:35
    #3 0x526921 in ColorChanger::start() /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/colorchanger.cpp:120:15
    #4 0x523b8d in main /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/podofocolor.cpp:116:12
    #5 0x7fc9a444f78f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #6 0x4300e8 in _start (/usr/bin/podofocolor+0x4300e8)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/portage/app-text/podofo-0.9.5/work/podofo-0.9.5/tools/podofocolor/graphicsstack.h:29:11 in GraphicsStack::TGraphicsStackElement::~TGraphicsStackElement()
==7677==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-2017-6841

Reproducer:
https://github.com/asarubbo/poc/blob/master/00216-podofo-nullptr-graphicsstack-h

Timeline:
2017-03-01: bug discovered
2017-03-02: bug reported to 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 GraphicsStack::TGraphicsStackElement::~TGraphicsStackElement (graphicsstack.h)

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