How severe is CVE-2026-8971?

CVE-2026-8971 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-2026-8971 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-8971?

CVE-2026-8971 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-8971?

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

Does CVE-2026-8971 have an EU (EUVD) identifier?

Yes. CVE-2026-8971 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30919.

When was CVE-2026-8971 published?

CVE-2026-8971 was published on 2026-05-19 and last updated on 2026-06-17.

CVE-2026-8971

CVE-2026-8971 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-346.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30919
Weakness: CWE-346
Affected product: Mozilla Firefox
Published: 2026-05-19
Last modified: 2026-06-17

Description

Same-origin policy bypass in the Networking: JAR component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

Frequently asked questions

What is CVE-2026-8971?: Same-origin policy bypass in the Networking: JAR component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.
How severe is CVE-2026-8971?: CVE-2026-8971 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-2026-8971 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-8971?: CVE-2026-8971 primarily affects Mozilla Firefox. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-8971?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-8971 have an EU (EUVD) identifier?: Yes. CVE-2026-8971 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30919.
When was CVE-2026-8971 published?: CVE-2026-8971 was published on 2026-05-19 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

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