Review reviewHigh
CVE-2026-8963
Mozilla Firefox, Thunderbird, firefox
Spoofing issue in the Web Speech component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.
- CVSS
- 7.5
- EPSS
- - - percentile
- CISA KEV
- Not listed
- Published
- 2026.05.19
Review review
The CVSS severity warrants an early asset and exposure review.
Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 7.5
Vulnerability overview
Spoofing issue in the Web Speech component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.
Affected product and versions
- Product
- Mozilla Firefox, Thunderbird, firefox
- Affected versions
- < 151.0.0
- Fixed versions
- 151.0.0
Recommended response sequence
Confirm exposure before applying a vendor-supported change.
- 1Identify
Confirm that Mozilla Firefox, Thunderbird, firefox and an affected version are present.
- 2Prioritize
Combine exploitation signals with asset exposure and business criticality.
- 3Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
- 4Verify
Recheck the version, service health, access paths, and relevant logs.
Technical data
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CWE
- CWE-290