CVE-2021-45394 is a high-severity (CVSS 8.8) Deserialization of Untrusted Data vulnerability in spipu/html2pdf. 1 public exploit reference exists, so weaponization risk is real. A fix is available for spipu/html2pdf — see the affected versions and patch details below.
Cross-site Scripting in HTML2PDF
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-45394 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
spipu/html2pdfReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
An issue was discovered in Spipu HTML2PDF before 5.2.4. Attackers can trigger deserialization of arbitrary data via the injection of a malicious <link> tag in the converted HTML document.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | spipu/html2pdf | all versions | 5.2.4composer require spipu/html2pdf:^5.2.4 |
Affected Products
html2pdfhtml2pdf_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for spipu/html2pdf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update spipu/html2pdf to 5.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-45394 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.
Frequently Asked Questions
Is CVE-2021-45394 in your dependencies?
Find it across Packagist, including transitive dependencies.