GStreamer is a library for constructing graphs of media-handling components. An integer underflow has been detected in the function qtdemux_parse_theora_extension within qtdemux.c. The vulnerability occurs due to an underflow of the gint size variable, which causes size to hold a large unintended value when cast to an unsigned integer. This 32-bit negative value is then cast to a 64-bit unsigned integer (0xfffffffffffffffa) in a subsequent call to gst_buffer_new_and_alloc. The function gst_buffer_new_allocate then attempts to allocate memory, eventually calling _sysmem_new_block. The function _sysmem_new_block adds alignment and header size to the (unsigned) size, causing the overflow of the 'slice_size' variable. As a result, only 0x89 bytes are allocated, despite the large input size. When the following memcpy call occurs in gst_buffer_fill, the data from the input file will overwrite the content of the GstMapInfo info structure. Finally, during the call to gst_memory_unmap, the ove…