VulnerabilityModified
CVE-2021-4138
Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.
MEDIUM 5.3EPSS 0.85%
Does this matter?
Lower severity and a low EPSS score (0.85%). Track it; it rarely justifies an emergency change on its own.
Description
Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.
- CVSS 3.1
- 5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- EPSS
- 0.85% probability · 58th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- mozilla/geckodriver
- Source
- security@mozilla.org
EPSS 0.8% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1652612Issue Tracking, Permissions Required, Third Party Advisory
- https://github.com/mozilla/geckodriver/releases/tag/v0.30.0Release Notes, Third Party Advisory
- https://bugzilla.mozilla.org/show_bug.cgi?id=1652612Issue Tracking, Permissions Required, Third Party Advisory
- https://github.com/mozilla/geckodriver/releases/tag/v0.30.0Release Notes, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.