CVE-2026-55798 python-pillow CVE debrief

Who should care

Users of Pillow library on Windows systems, operators of affected deployments, platform administrators, vulnerability management teams, and security teams should be aware of this vulnerability and take necessary actions to mitigate it.

Technical summary

Pillow is a Python imaging library. Prior to 12.3.0, WindowsViewer.get_command() constructed a cmd.exe shell command by directly embedding a file path into an f-string without escaping and passed the result to subprocess.Popen(..., shell=True), allowing shell metacharacters in the file path to inject arbitrary cmd.exe commands. This issue is fixed in version 12.3.0. Users of Pillow library on Windows systems should update to version 12.3.0 or later to mitigate this vulnerability. The vulnerability has a CVSS score of 4.5 and is classified as MEDIUM severity.

Defensive priority

Medium priority due to CVSS score of 4.5 and potential for local attack.

Recommended defensive actions

• Update Pillow to version 12.3.0 or later
• Review and validate file paths used in WindowsViewer.get_command()
• Implement additional input validation and sanitization for file paths
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• 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

Evidence notes

The CVE record and NVD entry provide details on the vulnerability and its fix. Release notes and patch commits are available. The vulnerability allows for arbitrary cmd.exe commands due to improper escaping of file paths in WindowsViewer.get_command(). Users should verify their deployments and review official advisories for affected scope and severity. Defensive measures include updating Pillow to version 12.3.0 or later and implementing additional input validation and sanitization for file paths.

Official resources