How severe is CVE-2021-21029?

CVE-2021-21029 has a CVSS score of 4.8/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-21029?

CVE-2021-21029 affects the following packages: magento/community-edition (Packagist), magento/community-edition (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-21029?

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.

How do I detect CVE-2021-21029 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for magento/community-edition. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-21029 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2021-21029?

O3 pinpoints whether CVE-2021-21029 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-21029 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-21029 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-21029?

CVE-2021-21029 has an EPSS (Exploit Prediction Scoring System) score of 84.7%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is CVE-2021-21029?

CVE-2021-21029 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-21029 published, and has it been updated?

CVE-2021-21029 was published on February 11, 2021 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2021-21029: magento/community-edition Cross-Site Scripting…

EPSS Exploitation Probability

via FIRST.org ↗

84.7%probability of exploitation in next 30 days

Very High Risk100th percentile+41.17%

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.

Blast Radius

2 pkgs affected

🐘magento/community-edition🐘magento/community-edition

Real-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

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`magento/community-edition`	all versions	2.3.6-p1
🐘Packagist	`magento/community-edition`	≥ 2.4.0&&< 2.4.2	2.4.2

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for magento/community-edition. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 pinpoints whether CVE-2021-21029 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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

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.

O3 Security · Impact-Aware SCA

Is CVE-2021-21029 in your dependencies?

O3 detects CVE-2021-21029 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2021-21029