How severe is CVE-2025-5271?

CVE-2025-5271 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 no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2025-5271 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-5271?

CVE-2025-5271 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-5271?

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

Does CVE-2025-5271 have an EU (EUVD) identifier?

Yes. CVE-2025-5271 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-18105.

When was CVE-2025-5271 published?

CVE-2025-5271 was published on 2025-05-27 and last updated on 2026-06-17.

CVE-2025-5271

CVE-2025-5271 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. The underlying weakness is classified as CWE-116.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-18105
Weakness: CWE-116
Affected product: Mozilla Firefox
Published: 2025-05-27
Last modified: 2026-06-17

Description

Previewing a response in Devtools ignored CSP headers, which could have allowed content injection attacks. This vulnerability was fixed in Firefox 139 and Thunderbird 139.

Frequently asked questions

What is CVE-2025-5271?: Previewing a response in Devtools ignored CSP headers, which could have allowed content injection attacks. This vulnerability was fixed in Firefox 139 and Thunderbird 139.
How severe is CVE-2025-5271?: CVE-2025-5271 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 no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2025-5271 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-5271?: CVE-2025-5271 affects Mozilla Firefox. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-5271?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-5271 have an EU (EUVD) identifier?: Yes. CVE-2025-5271 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-18105.
When was CVE-2025-5271 published?: CVE-2025-5271 was published on 2025-05-27 and last updated on 2026-06-17.

References

Affected products (1)

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

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