Summary
WeasyPrint has CSS Injection via Presentational Hints
Full technical description
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
CVE-2026-49452 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
- Escape attribute values before embedding into CSS
- Restrict allowed values for presentational hints
VULN-05_css_injection_presentational_hints.md
Frequently Asked Questions
- What is CVE-2026-49452? CVE-2026-49452 is a medium-severity security vulnerability in weasyprint (pip), affecting versions <= 68.1. No fixed version is listed yet.
- How severe is CVE-2026-49452? CVE-2026-49452 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of weasyprint are affected by CVE-2026-49452? weasyprint (pip) versions <= 68.1 is affected.
- Is there a fix for CVE-2026-49452? No fixed version is listed for CVE-2026-49452 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2026-49452 exploitable, and should I be worried? Whether CVE-2026-49452 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-49452 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.