CVE-2021-4138
MEDIUMCVSS 5.3/10EPSS 0.77%
Last modified
CVE-2021-4138 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.. EPSS estimates a 0.77% chance of exploitation in the next 30 days.
Description
Improved Host header checks to reject requests not sent to a well-known local hostname or IP, or the server-specified hostname.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Geckodriver | < 0.30.0 |
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
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is 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.
How severe is CVE-2021-4138?
CVE-2021-4138 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.77% probability of exploitation in the next 30 days.
How do I fix CVE-2021-4138?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2021-4138?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST