CVE-2026-55798 Pillow: WindowsViewer.get_command() OS command injection via unescaped shell path

What is CVE-2026-55798?

CVE-2026-55798 is a medium-severity command injection vulnerability in Python Pillow, published on 6 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

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.

Weakness: CWE-78

Which versions are affected by CVE-2026-55798?

4 open source packages ship an affected version, including pillow and Pillow. It affects 1 product.

Products include Python Pillow.

How do I fix CVE-2026-55798?

Upgrade pillow to 12.3.0 or later.

Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.

Is CVE-2026-55798 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55798 exists.

Other vulnerabilities in Python Pillow

• CVE-2014-3007 Pillow command injection Critical 10.0
• CVE-2026-96639 Pillow multi-frame loaders can reuse stale native image storage after mode transitions Critical 9.8
• CVE-2022-30595 Buffer over-flow in Pillow Critical 9.8
• CVE-2021-25289 Out of bounds write in Pillow Critical 9.8
• CVE-2016-4009 Pillow Integer overflow in ImagingResampleHorizontal Critical 9.8

All Python Pillow vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-pillow-2026-55798, CLSA-2026-1787903381, CLSA-2026-1788345043, CLSA-2026-1788863918, ECHO-c51d-efb4-9117, GHSA-4x4j-2g7c-83w6 and 12 more.