CVE-2026-96636

Affected versions of the Pillow package are vulnerable to Improper Handling of Highly Compressed Data (Data Amplification) due to decompression-bomb protection being enforced only on the first frame of multi-frame images. The `MpoImageFile.seek()` and `DcxImageFile.seek()` methods re-parse subsequent frame headers and reassign `self._size` without invoking `Image._decompression_bomb_check`, unlike `GifImagePlugin` and `TiffImagePlugin`, which correctly re-check on every `seek()` call. An attacker can craft an MPO or DCX file whose first frame is small enough to pass the initial bomb check but whose later frame declares extremely large dimensions, so that when an application iterates frames via `seek()` and `load()` (e.g., thumbnailers or format converters), Pillow decodes the oversized frame and commits excessive memory, resulting in denial of service through memory exhaustion.