What’s Vulnerable › Vulnerabilities

CVE-2018-12395

• Severity: high (CVSS 7.5 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-02-28 · updated 2026-06-17

Description

By rewriting the Host: request headers using the webRequest API, a WebExtension can bypass domain restrictions through domain fronting. This would allow access to domains that share a host that are otherwise restricted. This vulnerability affects Firefox ESR < 60.3 and Firefox < 63.

Affected products

• Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 18.10
• Debian Linux: 8.0, 9.0
• Mozilla Firefox: before 63.0 — fixed in 63.0
• Mozilla Firefox ESR: before 60.3 — fixed in 60.3
• RedHat Enterprise Linux Desktop: 6.0, 7.0
• RedHat Enterprise Linux Server: 6.0, 7.0
• RedHat Enterprise Linux Server Eus: 7.5
• RedHat Enterprise Linux Workstation: 6.0, 7.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 63.0; Mozilla Firefox ESR 60.3. Check the vendor advisory for mitigations.

References

• http://www.securityfocus.com/bid/105718
• http://www.securitytracker.com/id/1041944
• https://access.redhat.com/errata/RHSA-2018:3005
• https://access.redhat.com/errata/RHSA-2018:3006
• https://bugzilla.mozilla.org/show_bug.cgi?id=1467523
• https://lists.debian.org/debian-lts-announce/2018/11/msg00008.html
• https://security.gentoo.org/glsa/201811-04
• https://usn.ubuntu.com/3801-1/
• https://www.debian.org/security/2018/dsa-4324
• https://www.mozilla.org/security/advisories/mfsa2018-26/
• https://www.mozilla.org/security/advisories/mfsa2018-27/
• http://www.securityfocus.com/bid/105718

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