How severe is CVE-2026-8963?

CVE-2026-8963 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-8963 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-8963?

CVE-2026-8963 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-2026-8963?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-8963 have an EU (EUVD) identifier?

Yes. CVE-2026-8963 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30914.

When was CVE-2026-8963 published?

CVE-2026-8963 was published on 2026-05-19 and last updated on 2026-06-17.

CVE-2026-8963

CVE-2026-8963 is a high-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 7.5. 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-290.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30914
Weakness: CWE-290
Affected product: Mozilla Firefox
Published: 2026-05-19
Last modified: 2026-06-17

Description

Spoofing issue in the Web Speech component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

Frequently asked questions

What is CVE-2026-8963?: Spoofing issue in the Web Speech component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.
How severe is CVE-2026-8963?: CVE-2026-8963 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-8963 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-8963?: CVE-2026-8963 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-2026-8963?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-8963 have an EU (EUVD) identifier?: Yes. CVE-2026-8963 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30914.
When was CVE-2026-8963 published?: CVE-2026-8963 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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