How severe is CVE-2021-38491?

CVE-2021-38491 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-38491 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-38491?

CVE-2021-38491 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-38491?

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

When was CVE-2021-38491 published?

CVE-2021-38491 was published on 2021-11-03 and last updated on 2026-06-17.

CVE-2021-38491

CVE-2021-38491 is a medium-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Mozilla Firefox
Published: 2021-11-03
Last modified: 2026-06-17

Description

Mixed-content checks were unable to analyze opaque origins which led to some mixed content being loaded. This vulnerability affects Firefox < 92.

Frequently asked questions

What is CVE-2021-38491?: Mixed-content checks were unable to analyze opaque origins which led to some mixed content being loaded. This vulnerability affects Firefox < 92.
How severe is CVE-2021-38491?: CVE-2021-38491 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-38491 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-38491?: CVE-2021-38491 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-38491?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-38491 published?: CVE-2021-38491 was published on 2021-11-03 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

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