How severe is CVE-2021-39318?

CVE-2021-39318 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-39318 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39318?

CVE-2021-39318 affects H5p-css-editor Project H5p-css-editor. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-39318?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-39318 published?

CVE-2021-39318 was published on 2021-12-14 and last updated on 2026-06-17.

CVE-2021-39318

CVE-2021-39318 is a medium-severity vulnerability in H5p-css-editor Project H5p-css-editor with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 1% (51st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: H5p-css-editor Project H5p-css-editor
Published: 2021-12-14
Last modified: 2026-06-17

Description

The H5P CSS Editor WordPress plugin is vulnerable to Reflected Cross-Site Scripting via the h5p-css-file parameter found in the ~/h5p-css-editor.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 1.0.

Frequently asked questions

What is CVE-2021-39318?: The H5P CSS Editor WordPress plugin is vulnerable to Reflected Cross-Site Scripting via the h5p-css-file parameter found in the ~/h5p-css-editor.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 1.0.
How severe is CVE-2021-39318?: CVE-2021-39318 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-39318 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (51st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39318?: CVE-2021-39318 affects H5p-css-editor Project H5p-css-editor. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-39318?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-39318 published?: CVE-2021-39318 was published on 2021-12-14 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:h5p-css-editor_project:h5p-css-editor:*:*:*:*:*:wordpress:*:*

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