Kozea WeasyPrint up to 68.x CSS Processing __init__.py tinycss2.parse_blocks_contents Background server-side request forgery

Summaryinfo

A vulnerability marked as critical has been reported in Kozea WeasyPrint up to 68.x. This affects the function tinycss2.parse_blocks_contents of the file weasyprint/css/__init__.py of the component CSS Processing. Performing a manipulation of the argument Background results in server-side request forgery. This vulnerability is cataloged as CVE-2026-49452. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as critical, was found in Kozea WeasyPrint up to 68.x. This affects the function tinycss2.parse_blocks_contents of the file weasyprint/css/__init__.py of the component CSS Processing. The manipulation of the argument background with an unknown input leads to a server-side request forgery vulnerability. CWE is classifying the issue as CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

WeasyPrint helps web developers to create PDF documents. Prior to 69.0, WeasyPrint embeds unescaped HTML presentational-hint attribute values into CSS in weasyprint/css/__init__.py when presentational_hints=True. The background attribute is inserted into a background-image:url() declaration and parsed by tinycss2.parse_blocks_contents(), allowing untrusted HTML to inject additional CSS declarations. Applications that render untrusted HTML with presentational hints enabled can be affected by CSS injection and server-side requests through injected url() values. This issue is fixed in version 69.0.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-49452 since 05/30/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 69.0 eliminates this vulnerability.

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Productinfo

Vendor

• Kozea

Name

• WeasyPrint

Version

• 68.x

Website

• Product: https://github.com/Kozea/WeasyPrint/

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