CVE-2026-112393

Pillow is like a photo-processing toolkit that many websites and apps use behind the scenes to resize, convert, or save images. This bug is like a filing cabinet drawer that's slightly too small for the folder being put in it — if someone hands the system a specially crafted TIFF image, the drawer can overflow, potentially crashing the program or spilling bits of leftover data that were sitting nearby in memory. It only happens in a specific scenario: saving a TIFF image into memory (not directly to a file on disk).

This matters to you if your website, app, or internal software uses the Pillow Python image library to generate or convert TIFF images, particularly when saving them into memory rather than to a disk file. It's only a real risk if your system accepts TIFF image uploads or processes TIFF images from untrusted sources — if you never handle TIFF files this way, you're not exposed.

There is no evidence anyone is exploiting this in the wild, it isn't on any government list of actively-attacked vulnerabilities, and there's no public attack tool available for it. This is a routine fix-when-convenient situation, not an emergency — plan to update Pillow during normal maintenance.

Confirm exposure by auditing where Pillow's Image.save() is called with TIFF output targeting a file-like object without a real fileno() (e.g. io.BytesIO, in-memory buffers used for API responses or thumbnail generation) — file-path saves with genuine file descriptors are not affected. Upgrade Pillow to 13.0.0 or later across all affected branches (issue present from 2.0.0 through 13.0.0); review the Pillow changelog for breaking changes in the 11.x/12.x/13.x line before upgrading production dependencies. If immediate patching isn't possible, mitigate by routing untrusted TIFF processing through disk-based temp files instead of BytesIO, or by rejecting/validating TIFF uploads with strict tag/ICC-profile sanitization. There is no CISA KEV entry and no due date requirement. Monitor for crash reports or anomalous memory-disclosure behavior in image-processing workers as a precaution, and track Pillow security advisories for this CVE.

CWE-122 heap buffer overflow in libtiff's _tiffWriteProc callback as wired into Pillow; the allocation size is derived from the prior buffer position rather than the current write offset, so an attacker-controlled out-of-line TIFF tag or retained ICC profile can cause libtiff to write past the buffer after a forward seek, enabling a crash, stale-heap disclosure, or potentially code execution. Only triggered when saving compressed TIFF output to a target lacking a usable fileno() (e.g. BytesIO); file-path targets with real descriptors are unaffected. Not listed in CISA KEV, no public exploit code exists, and predicted exploitation likelihood is low with a flat trend — exploit maturity is theoretical/PoC-less at this time. Fixed upstream in Pillow 13.0.0.