Ubuntu publishes advisory USN-8999-1 covering Pillow flaws affecting image and font handling

What happened and what to do

Ubuntu Security published advisory USN-8999-1 on 4 November 2026, covering vulnerabilities in Pillow, a widely used Python image processing library. According to the advisory, the flaws can lead to information disclosure, denial of service, crashes or arbitrary code execution when processing images and files. Cases cited include McIdas AREA image loading, decompression bombs in font files and GD images, PDF streams without decompressed-size limits, EPS files with negative byte counts, JPEG2000 component widths, sort filter sizes, image coordinate calculations and colour management mode compatibility.

In practice, any service that receives user images or documents and processes them with Pillow may be exposed. A practical response starts with inventory: identify where the library runs, which versions are installed and which upload, conversion or thumbnail pipelines use it. Then apply the package updates indicated by the distribution, isolate processing of untrusted files in workers with memory and time limits, and monitor restarts and consumption spikes that could indicate exploitation attempts.

How the consultancy can help

Wendelmaques can diagnose your exposure to Pillow: version inventory, mapping of flows that receive third-party files and assessment of where to isolate processing. We then implement the update, isolated workers with resource limits and failure monitoring, on your own infrastructure.

Next step

If your company processes images, PDFs or fonts uploaded by users, send a short description of your case, including where the library is used, and receive a scoped proposal for diagnosis and implementation.