CVE-2026-59199 in Pillow
Pillow is a Python imaging library. Prior to 12.3.0, Pillow public image coordinate APIs can trigger a native heap out-of-bounds write when given coordinates near the signed 32-bit integer limits in Image.paste(), Image.crop(), or Image.alpha_composite(). This issue is fixed in version 12.3.0.
Quick answer
Python Pillow Pillow should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Pillow before 12.3.0
Fixed versions
- Pillow 12.3.0 or later
How to fix it
CVE-2026-59199 affects Pillow. In simple terms, a crafted file may break memory safety and may lead to code execution or a crash. Fix it by updating to Pillow 12.3.0 or later. If this system is online or used by admins, treat the fix as urgent.
- Find every place where Pillow is installed or used.
- Check if the version matches: Pillow before 12.3.0.
- Update or apply the vendor fix: Pillow 12.3.0 or later.
- If you cannot update today, allow only trusted users and trusted networks.
- Turn off the affected feature or plugin if the vendor says that is safe to do.
- Check logs for crashes, strange requests, new admin actions, or unexpected access.
- Change secrets or passwords if you think data or admin access may have been exposed.
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Verify the fix
- Confirm the installed version or mitigation matches: Pillow 12.3.0 or later.
- Confirm the affected feature is no longer exposed to untrusted users.
- Run the affected workflow again and make sure it still works.
- Review logs again after the fix for repeated suspicious activity.
- Run a new Fixnx scan if this software is part of a public website.
- Save the advisory link and proof of the fix in your change record.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-59199?
Python Pillow Pillow versions listed as affected should be reviewed: Pillow before 12.3.0.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.