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CVE-2018-12398

23
FAUCET Score

CVE-2018-12398 is a medium-severity vulnerability affecting Firefox versions prior to 63, including those on Canonical Ubuntu Linux. It allows an attacker to bypass Content Security Policy (CSP) by injecting stylesheets through specially crafted, reflected URLs in resource URIs like "chrome:". The attack requires user interaction (UI:R) but can lead to high integrity impact (I:H) without affecting confidentiality or availability. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
< 63.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
14.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
16.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
18.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
18.10CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

6.5MEDIUM

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.62%
Probability of exploitation in next 30 days
EPSS Percentile
73.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0162 is in the 86th percentile among its peer group of 26,234 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (4)

mozillavendor investigatingvia nvd_reference
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: firefox
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: firefox

Vendor Advisories (1)

redhatCVE-2018-12398Moderate

firefox: Content Security Policy bypass through stylesheet injection in resource URIs

Oct 23, 2018

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions RequiredVendor Advisory
bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions RequiredVendor Advisory
usn.ubuntu.com / 3801-1
Third Party Advisory
mozilla.org / security/advisories/mfsa2018-26
Vendor Advisory
securityfocus.com / bid/105721
Third Party AdvisoryVDB Entry
securitytracker.com / id/1041944
Third Party AdvisoryVDB Entry