Impact An out-of-bounds write may be triggered when loading a specially crafted PSD image. Pillow >= 10.3.0 users are affected.

Patches Pillow 12.1.1 will be released shortly with a fix for this.

Workarounds Image.open() has a formats parameter that can be used to prevent PSD images from being opened.

References Pillow 12.1.1 will add release notes at https://pillow.readthedocs.io/en/stable/releasenotes/index.html

Impact Pillow did not limit the amount of GZIP-compressed data read when decoding a FITS image, making it vulnerable to decompression bomb attacks. A specially crafted FITS file could cause unbounded memory consumption, leading to denial of service (OOM crash or severe performance degradation).

Patches The amount of data read is now limited to the necessary amount. Fixed in Pillow 12.2.0 (PR #9521).

Workarounds Avoid Pillow >= 10.3.0, < 12.2.0 Only open specific image formats, excluding FITS.

Impact Processing a malicious PSD file could lead to memory corruption, potentially resulting in a crash or arbitrary code execution.

Patches Patched version: 12.2.0

Pillow 12.1.1 addressed CVE-2026-25990 by adding checks for tile extents in PSD image decoding/encoding to prevent an out-of-bounds write. However, the bounds checks computed tile extent sums using types susceptible to integer overflow, meaning a PSD image with carefully chosen tile dimensions could produce values that wrap around and bypass the checks, still triggering an out-of-bounds write in src/decode.c and src/encode.c. The fix avoids adding extents together before comparison.

Workarounds Use any version but affected versions: >= 10.3.0, < 12.2.0

Resources - Fix: https://github.com/python-pillow/Pillow/pull/9520 - Original issue: CVE-2026-25990 (Pillow 12.1.1)