Summary
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.
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.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
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
Frequently Asked Questions
- What is CVE-2021-46875? CVE-2021-46875 is a high-severity cross-site scripting (XSS) vulnerability in ezsystems/ezpublish-kernel (composer), affecting versions <= 6.13.8.1. It is fixed in 6.13.8.2, 7.5.15.2, 1.2.5.1, 1.3.1.1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which packages are affected by CVE-2021-46875?
ezsystems/ezpublish-kernel(composer) (versions <= 6.13.8.1)ezsystems/ezplatform-kernel(composer) (versions <= 1.2.5)
- Is there a fix for CVE-2021-46875? Yes. CVE-2021-46875 is fixed in 6.13.8.2, 7.5.15.2, 1.2.5.1, 1.3.1.1. Upgrade to this version or later.
- Is CVE-2021-46875 exploitable, and should I be worried? Whether CVE-2021-46875 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-46875 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-46875?
- Upgrade
ezsystems/ezpublish-kernelto 6.13.8.2 or later - Upgrade
ezsystems/ezpublish-kernelto 7.5.15.2 or later - Upgrade
ezsystems/ezplatform-kernelto 1.2.5.1 or later - Upgrade
ezsystems/ezplatform-kernelto 1.3.1.1 or later
- Upgrade