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CVE-2018-5121

18
FAUCET Score

CVE-2018-5121 describes a domain name spoofing vulnerability affecting Firefox versions prior to 58 on macOS. Specifically, low descenders on certain Tibetan characters rendered in the address bar are clipped, which can be exploited in Internationalized Domain Names (IDNs) to visually impersonate legitimate domains. With a CVSS score of 5.3 (Medium), this vulnerability has a low attack complexity and requires no user interaction, but its impact is limited to information integrity (spoofing). There is no evidence of active exploitation, public exploit code, or significant community discussion, and it is not listed in CISA's KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
<= 57.0.4CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 58CPE match
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.47%
Probability of exploitation in next 30 days
EPSS Percentile
71.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0147 is in the 53rd percentile among its peer group of 23,723 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

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

Remediation

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions Required
mozilla.org / security/advisories/mfsa2018-02
Vendor Advisory
securityfocus.com / bid/102786
Third Party AdvisoryVDB Entry
securitytracker.com / id/1040270
Third Party AdvisoryVDB Entry