CVE-2021-46875
Fix: ezsystems/ezpublish-kernel@29fecd2CVE-2021-46875 is a Cross-site Scripting (XSS) vulnerability in ezsystems/ezpublish-kernel. O3 Security confirms whether CVE-2021-46875 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-site scripting in eZ Platform Kernel
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-2021-46875.
Real-World Exposure
ezsystems/ezpublish-kernel🐘ezsystems/ezpublish-kernel🐘ezsystems/ezplatform-kernel🐘ezsystems/ezplatform-kernelReal-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
Impact
In file upload it is possible by certain means to upload files like .html and .js. These may contain XSS exploits which will be run when links to them are accessed by victims.
Patches
The fix consists simply of adding common types of scriptable file types to the configuration of the already existing filetype blacklist feature. See "Patched versions". As such, this can also be done manually, without installing the patched versions. This may be relevant if you are currently running a considerably older version of the kernel package and don't want to upgrade it at this time. Please see the settting "ezsettings.default.io.file_storage.file_type_blacklist" at: https://github.com/ezsystems/ezplatform-kernel/blob/master/eZ/Bundle/EzPublishCoreBundle/Resources/config/default_settings.yml#L109
Important note
You should adapt this setting to your needs. Do not add file types to the blacklist that you actually need to be able to upload. For instance, if you need your editors to be able to upload SVG files, then don't blacklist that. Instead, you could e.g. use an approval workflow for such content.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | ezsystems/ezpublish-kernel | all versions | 6.13.8.2 |
| 🐘Packagist | ezsystems/ezpublish-kernel | ≥ 7.0.0&&< 7.5.15.2 | 7.5.15.2 |
| 🐘Packagist | ezsystems/ezplatform-kernel | all versions | 1.2.5.1 |
| 🐘Packagist | ezsystems/ezplatform-kernel | ≥ 1.3.0&&< 1.3.1.1 | 1.3.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ezsystems/ezpublish-kernel. 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 ezsystems/ezpublish-kernel to 6.13.8.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-46875 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-2021-46875 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-2021-46875. 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-2021-46875 in your dependencies?
O3 detects CVE-2021-46875 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.