CVE-2021-21029 — magento/community-edition
MEDIUMCVE-2021-21029 is a medium-severity (CVSS 4.8) Cross-site Scripting (XSS) vulnerability in magento/community-edition. EPSS puts its 30-day exploitation probability at 84.6% (100th percentile). A fix is available for magento/community-edition — see the affected versions and patch details below.
Magento Reflected Cross-site Scripting vulnerability via 'file' parameter
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-2021-21029 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 377,166 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
magento/community-edition🐘magento/community-editionReal-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
Magento versions 2.4.1 (and earlier), 2.4.0-p1 (and earlier) and 2.3.6 (and earlier) are affected by a Reflected Cross-site Scripting vulnerability via 'file' parameter. Successful exploitation could lead to arbitrary JavaScript execution in the victim's browser. Access to the admin console is required for successful exploitation.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | magento/community-edition | all versions | 2.3.6-p1composer require magento/community-edition:^2.3.6-p1 |
| 🐘Packagist | magento/community-edition | ≥ 2.4.0&&< 2.4.2 | 2.4.2composer require magento/community-edition:^2.4.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for magento/community-edition, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update magento/community-edition to 2.3.6-p1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21029 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-2021-21029 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21029. 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-2021-21029 in your dependencies?
O3 Security finds CVE-2021-21029 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.