This is a high-severity Pillow security advisory for CVE-2026-112902. A malicious TIFF (or EXIF metadata in a JPEG/PNG/WebP) can cause Pillow to leak process memory or crash when the image is re-saved as a TIFF.

Pillow incorrectly forwards unknown TIFF tags to libtiff, assuming its own registration controls how libtiff interprets the arguments. It does not; libtiff uses its built-in definition for known tags.

As a result, a tiny crafted file—about 356 bytes in the reproducer—can make Pillow copy up to attacker-chosen amounts of worker-process memory into the output TIFF, or trigger a segmentation fault.

The vulnerable code path is triggered by an ordinary Image.open() followed by im.save(fp, "TIFF"), especially when the source image is compressed and therefore uses libtiff.

## Impact
Confidentiality: Memory contents can be disclosed in the saved TIFF metadata; the report says this can expose data from Python, libc, libtiff, libjpeg, and other linked libraries, potentially defeating ASLR.

Availability: Certain crafted tags cause a deterministic worker crash (SIGSEGV) from a sub-1 KB upload.

Scope: Services that accept image uploads and convert or re-save them as TIFF are most exposed; JPEG/PNG/WebP EXIF metadata preserved during TIFF conversion can also trigger it.

The advisory found only out-of-bounds reads, not writes.

Affected versions and fix
Item	Detail
Package	Pillow (pip)
Vulnerable versions	12.3.0 and earlier
Fixed version	13.0.0
Severity	High, CVSS v4 8.7/10
CVE / GHSA	CVE-2026-112902 / GHSA-xvh5-g6gv-559v

Upgrade Pillow to 13.0.0 or later as soon as possible. If immediate upgrade is not possible, avoid accepting and re-encoding untrusted images as TIFF, and do not pass untrusted tiffinfo/EXIF metadata into TIFF saves.