A signed integer overflow vulnerability in ImageMagick's SIXEL decoder allows an attacker to trigger memory corruption and denial of service when processing a maliciously crafted SIXEL image file. The vulnerability occurs during buffer reallocation operations where pointer arithmetic using signed 32-bit integers overflows.

AddressSanitizer:DEADLYSIGNAL
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==143838==ERROR: AddressSanitizer: UNKNOWN SIGNAL on unknown address 0x000000000000
  #0 0x7f379d5adb53 (/lib/x86 64-linux-gnu/libc.so.6+0xc4b53)