CVE-2026-112405

Summary

Image.merge() checks the mode of every input band except band 0. If band 0 is a single-band I or F image, the native merge routine reads a pixel pointer that is NULL for those modes and the process crashes. The IPTC plugin reaches this from a plain Image.open() followed by a load, and IPTC has no magic-byte prefilter, so a crafted file with no recognizable header can drive it.

Details

The validation loop skips band 0:

• src/PIL/Image.py:3795 iterates for band in bands[1:] and checks mode and size only for those.

For an I or F image the 8-bit plane image8 is NULL (only image32 is set). ImagingMerge dereferences bands[0]->image8[y] for the multi-band output modes:

• src/libImaging/Bands.c:302, :311, :321

The IPTC loader builds the band list from an attacker-typed sub-image and passes it to merge with the sub-image at index 0:

• src/PIL/IptcImagePlugin.py:156-160
• src/PIL/IptcImagePlugin.py:169 registers the opener with no accept function.

PoC

from PIL import Image

# Band 0 is a single-band "I" image: its image8 plane is NULL. merge() validates only
# bands[1:], so the native ImagingMerge dereferences the NULL plane for band 0.
band0 = Image.new("I", (4, 4))
Image.merge("RGB", [band0, Image.new("L", (4, 4)), Image.new("L", (4, 4))])

Run it:

$ python 02_poc.py
Segmentation fault (core dumped)

Observed on a source build of commit 3e2ab96.

Under AddressSanitizer:

==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000
    #0 ImagingMerge   src/libImaging/Bands.c:311
    #1 _merge         src/_imaging.c:2492
SUMMARY: AddressSanitizer: SEGV src/libImaging/Bands.c:311 in ImagingMerge

The null address confirms the dereference of the missing image8 plane for band 0.

Impact

NULL pointer dereference in a C extension. A crafted file opened and loaded through the IPTC path crashes the worker process. This is a hard crash, not a Python exception an application can catch.

Pillow is a Python imaging library. From 12.0.0 until 13.0.0, Pillow's Image.merge() can dereference a null image8 plane. Validation skips the first input band, allowing a 32-bit integer or floating-point image backed by image32 storage to be merged as a narrower multiband image. A crafted IPTC file can reach this path when an application opens and loads it, or a caller can invoke Image.merge() directly with such a first band. This causes a native process crash. This issue is fixed in version 13.0.0.

Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems.

Security Fix(es):

• pillow: Pillow: Denial of Service via unbounded recursion in PDF parser (CVE-2026-112391)

• pillow: pillow: Denial of service via double free during image transformation (CVE-2026-112402)

• pillow: pillow: Denial of Service via zero-size images in rank filters (CVE-2026-112392)

• pillow: pillow: Denial of Service via out-of-bounds memory access on zero-width images (CVE-2026-112397)

• pillow: Pillow: Denial of Service via null pointer dereference in Image.merge() (CVE-2026-112405)

• pillow: pillow: Denial of Service via crafted multi-frame image conversion (CVE-2026-112894)

• pillow: pillow: Denial of service via crafted PDF during append operations (CVE-2026-112895)

• pillow: pillow: Denial of Service via infinite loop during PDF page rewriting (CVE-2026-112406)

• pillow: pillow: Denial of Service via duplicate page references in PDF files (CVE-2026-96640)

• pillow: pillow: Denial of Service via unbounded memory expansion in MSP image decoder (CVE-2026-112892)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Pillow is a Python imaging library. From 12.0.0 until 13.0.0, Pillow's Image.merge() can dereference a null image8 plane. Validation skips the first input band, allowing a 32-bit integer or floating-point image backed by image32 storage to be merged as a narrower multiband image. A crafted IPTC file can reach this path when an application opens and loads it, or a caller can invoke Image.merge() directly with such a first band. This causes a native process crash. This issue is fixed in version 13.0.0.

Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems.

Security Fix(es):

• pillow: Pillow: Denial of Service via unbounded recursion in PDF parser (CVE-2026-112391)
• pillow: pillow: Denial of service via double free during image transformation (CVE-2026-112402)
• pillow: pillow: Denial of Service via zero-size images in rank filters (CVE-2026-112392)
• pillow: pillow: Denial of Service via out-of-bounds memory access on zero-width images (CVE-2026-112397)
• pillow: Pillow: Denial of Service via null pointer dereference in Image.merge() (CVE-2026-112405)
• pillow: pillow: Denial of Service via crafted multi-frame image conversion (CVE-2026-112894)
• pillow: pillow: Denial of service via crafted PDF during append operations (CVE-2026-112895)
• pillow: pillow: Denial of Service via infinite loop during PDF page rewriting (CVE-2026-112406)
• pillow: pillow: Denial of Service via duplicate page references in PDF files (CVE-2026-96640)
• pillow: pillow: Denial of Service via unbounded memory expansion in MSP image decoder (CVE-2026-112892)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Pillow is a Python imaging library. From 12.0.0 until 13.0.0, Pillow's Image.merge() can dereference a null image8 plane. Validation skips the first input band, allowing a 32-bit integer or floating-point image backed by image32 storage to be merged as a narrower multiband image. A crafted IPTC file can reach this path when an application opens and loads it, or a caller can invoke Image.merge() directly with such a first band. This causes a native process crash. This issue is fixed in version 13.0.0.

TuxCare rebuilt pillow to address 1 CVE. Fixed in 11.3.0.post13+tuxcare.

TuxCare rebuilt pillow to address 1 CVE. Fixed in 11.2.1.post15+tuxcare.

TuxCare rebuilt pillow to address 1 CVE. Fixed in 10.4.0.post18+tuxcare.

Root has patched CVE-2026-112405 in the pillow package for Root:PyPI. Multiple fixed versions available.

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).