CVE-2026-59197 python-pillow CVE debrief

Who should care

Users of Pillow, especially those using versions prior to 12.3.0, should be aware of this vulnerability and take steps to mitigate it. This includes reviewing and validating input to the rank-filter API and monitoring for potential exploitation attempts.

Technical summary

The vulnerability exists in Pillow's public rank-filter API. When given a very large odd filter size, ImageFilter.RankFilter.filter() calls image.expand(size // 2, size // 2) before rank-filter size validation. This can trigger a native heap out-of-bounds write due to unchecked signed int arithmetic in ImagingExpand(). The issue is fixed in version 12.3.0. Defensive priority should be given to updating Pillow to version 12.3.0 or later.

Defensive priority

High priority should be given to updating Pillow to version 12.3.0 or later.

Recommended defensive actions

• Update Pillow to version 12.3.0 or later
• Review and validate input to the rank-filter API
• Monitor for potential exploitation attempts
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-14T17:17:14.487Z and was last modified on 2026-07-21T19:17:11.907Z. The NVD entry is currently Modified. This information is based on the provided source corpus. Further verification is recommended to ensure accuracy.

Official resources