CVE-2021-4138: Mozilla Geckodriver

Medium severity, CVSS 5.3. EPSS: 0.8% chance of exploitation in the next 30 days.

Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.

Affected products

• Mozilla Geckodriver: before 0.30.0 (fixed in 0.30.0)

Published 2022-05-02. Last modified 2026-06-17.