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GHSA-jhhc-3hcp-qhm5

MediumCVSS 6.5 / 10

Published Jul 6, 2026·Last modified Jul 6, 2026

Affected Components(0)

No affected components available

Description

Summary

A CSS injection issue exists in WeasyPrint when HTML presentational hints are enabled. Unescaped attribute values are embedded into CSS, allowing injection of arbitrary CSS declarations. This affects applications processing untrusted HTML input.

Details

File: weasyprint/css/init.py

The background attribute is used to construct CSS:

background-image:url({element.get("background")})

This string is parsed by tinycss2.parse_blocks_contents().

Because the value is not escaped, additional CSS declarations can be injected.

PoC

Impact

CSS injection
Server-side requests via injected url()
Limited to cases where presentational_hints=True

Suggested Fix

Escape attribute values before embedding into CSS
Restrict allowed values for presentational hints VULN-05_css_injection_presentational_hints.md

Risk Scores

Base Score

6.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence

6.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS

N/A

Probability that this vulnerability will be exploited in the wild within the next 30 days.

Exploit

Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

Related Vulnerabilities

CVE-2026-49452
Alias

Browse More

Medium severity

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