CVE-2021-3841 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in sylius/sylius. A fix is available for sylius/sylius — see the affected versions and patch details below.
Cross site scripting in sylius/sylius
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-3841.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-3841 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
sylius/sylius🐘sylius/sylius🐘sylius/syliusReal-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
sylius/sylius versions prior to 1.9.10, 1.10.11, and 1.11.2 are vulnerable to stored cross-site scripting (XSS) through SVG files. This vulnerability allows attackers to inject malicious scripts that can be executed in the context of the user's browser.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | sylius/sylius | all versions | 1.9.10composer require sylius/sylius:^1.9.10 |
| 🐘Packagist | sylius/sylius | ≥ 1.10.0&&< 1.10.11 | 1.10.11composer require sylius/sylius:^1.10.11 |
| 🐘Packagist | sylius/sylius | ≥ 1.11.0&&< 1.11.2 | 1.11.2composer require sylius/sylius:^1.11.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sylius/sylius, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update sylius/sylius to 1.9.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3841 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-3841 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-3841. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-3841 in your dependencies?
O3 Security finds CVE-2021-3841 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.