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fkie_cve-2026-106443

WeasyPrint helps web developers to create PDF documents. Prior to 70.0, the image-loading path in weasyprint/images.py passes fetched image bytes from HTML img URLs, CSS image values, SVG image references, and data URIs to Pillow's generic image dispatcher without excluding EPS or PostScript formats. On hosts with Ghostscript installed, Pillow EpsImagePlugin invokes the interpreter for attacker-controlled PostScript, which can produce interpreter-permitted effects and can lead to remote code execution when the installed Ghostscript version has a usable sandbox bypass. Hosts without Ghostscript do not reach this rasterization path. This issue is fixed in version 70.0.

GHSA-r543-q48m-4c9j — WeasyPrint: EPS images reach the Ghostscript interpreter resulting in RCE

Affected: PyPI: WeasyPrint

### Summary

This was found during a pentest, funded by the NLNnet foundation, conducted by Stefan Vink from Radically Open Security and the only High issue found.

WeasyPrint passes fetched image bytes directly to Pillow's generic format dispatcher without restricting the input format. When Ghostscript is installed on the host, Pillow's EpsImagePlugin invokes it to rasterize attacker-controlled EPS/PS input. Any content that can supply an image to WeasyPrint (an <img> URL, CSS image value, SVG image reference, or data URI) can therefore drive untrusted PostScript into an external interpreter. On hosts running a Ghostscript version with a known -dSAFER bypass, this yields remote code execution.

### Details

The image pipeline reads an external response and hands the raw bytes to Pillow's format-agnostic Image.open, with no allowlist of safe raster formats:

with fetch(url_fetcher, url) as response: bytestring = response.read() mime_type = forced_mime_type or response.content_type

...

pillow_image = Image.open(BytesIO(bytestring))

Pillow selects the handler from the byte signature. For EPS/PS input it selects PIL.EpsImagePlugin, which invokes Ghostscript to rasterize the input when a Ghostscript executable is available. Modern Ghostscript builds may run with -dSAFER, but that does not remove the interpreter boundary — it only constrains it, and multiple CVEs have bypassed it.

The defect in WeasyPrint is that it dispatches untrusted bytes to a format handler capa…

UBUNTU-CVE-2026-106443

Affected: Ubuntu:20.04:LTS: weasyprint, Ubuntu:22.04:LTS: weasyprint, Ubuntu:24.04:LTS: weasyprint, Ubuntu:26.04:LTS: weasyprint

(WeasyPrint helps web developers to create PDF documents. Prior to 70.0 ...)