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Fencer Vulns
high 7.5

CVE-2018-12395 json

By rewriting the Host: request headers using the webRequest API, a WebExtension can bypass domain restrictions through domain fronting.

published 2019-02-28 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-4369

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.9%
EPSS 2.9% chance of exploitation in 30 days, percentile 86%
public exploits
0
none known

Summary

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.

Patch / fix

  • Mozilla Firefox ESR 60.3
  • Mozilla Firefox 63
  • firefox-esr Debian 14, Debian 13, Debian 12 60.3.0esr-1

debian advisories DEBIAN-CVE-2018-12395

  • firefox Ubuntu 14.04 LTS 63.0+build2-0ubuntu0.14.04.2
  • firefox Ubuntu 16.04 LTS 63.0+build2-0ubuntu0.16.04.2
  • firefox Ubuntu 18.04 LTS 63.0+build2-0ubuntu0.18.04.2

ubuntu advisories UBUNTU-CVE-2018-12395

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox RHEL 6 60.3.0-1.el6
  • firefox RHEL 7 60.3.0-1.el7_5

red hat advisories RHSA-2018:3006RHSA-2018:3005

  • MozillaFirefox SLES 12 SP4, SLES 12 SP3, SLES 12 SP2-BCL +13 more 60.3.0-109.50.2
  • MozillaFirefox SLE Module for Desktop Applications 15 60.3.0-3.17.1

suse advisories SUSE-SU-2018:3749-3SUSE-SU-2018:3749-2SUSE-SU-2018:3749-1SUSE-SU-2018:3656-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1

  • firefox Arch Linux 63.0-1

arch linux advisories AVG-787

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-12395 updated cvss 7.5

Mozilla: WebExtension bypass of domain restrictions through header rewriting

  • Red Hat Enterprise Linux Client (v. 7) firefox 60.3.0-1.el7_5 Red Hat Enterprise Linux Client Optional (v. 7) firefox 60.3.0-1.el7_5
    fixed: vendor fix RHSA-2018:3005
  • Red Hat Enterprise Linux Desktop (v. 6) firefox 60.3.0-1.el6 Red Hat Enterprise Linux Desktop Optional (v. 6) firefox 60.3.0-1.el6
    fixed: vendor fix RHSA-2018:3006
  • Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server (v. 7) firefox 60.3.0-1.el7_5
    fixed: vendor fix RHSA-2018:3005
  • Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox 60.3.0-1.el6 Red Hat Enterprise Linux Server (v. 6) firefox 60.3.0-1.el6
    fixed: vendor fix RHSA-2018:3006
  • Red Hat Enterprise Linux Server (v. 7) firefox 60.3.0-1.el7_5
    fixed: vendor fix RHSA-2018:3005
  • Red Hat Enterprise Linux Server Optional (v. 6) firefox 60.3.0-1.el6
    fixed: vendor fix RHSA-2018:3006
  • Red Hat Enterprise Linux Server Optional (v. 7) firefox 60.3.0-1.el7_5
    fixed: vendor fix RHSA-2018:3005
  • Red Hat Enterprise Linux Workstation (v. 6) firefox 60.3.0-1.el6
    fixed: vendor fix RHSA-2018:3006
show 4 more
  • Red Hat Enterprise Linux Workstation (v. 7) firefox 60.3.0-1.el7_5
    fixed: vendor fix RHSA-2018:3005
  • Red Hat Enterprise Linux Workstation Optional (v. 6) firefox 60.3.0-1.el6
    fixed: vendor fix RHSA-2018:3006
  • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 60.3.0-1.el7_5
    fixed: vendor fix RHSA-2018:3005
  • Red Hat Enterprise Linux 6 thunderbird Red Hat Enterprise Linux 7 thunderbird Red Hat Enterprise Linux 8 firefox, thunderbird
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.85% chance of exploitation in the next 30 days, higher than 86% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N

Affected products

  • Mozilla Firefox ESR
  • Mozilla Firefox

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.