CVE-2026-96637

Affected versions of the Pillow package are vulnerable to Improper Handling of Highly Compressed Data (Data Amplification) due to a missing decompression bomb check on an alternate image-loading path. The `SpiderImageFile.seek()` method computes an attacker-influenced frame offset and calls `self._open()` directly rather than through `Image.open()`, causing `self._size` to be reassigned from unvalidated header fields (`nsam`, `nrow`) without ever invoking `Image._decompression_bomb_check()`, unlike sibling multi-frame plugins such as `GifImagePlugin` and `TiffImagePlugin`. An attacker can craft a SPIDER stack file under 1KB whose second frame header declares an extremely large image size, causing `ImageFile.load_prepare()` to call `Image.core.new()` with the unchecked dimensions and allocate multiple gigabytes of memory upon `im.load()`, resulting in a Denial of Service.