SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityModified

CVE-2018-5121

This vulnerability affects Firefox < 58.

MEDIUM 5.3EPSS 1.44%

Does this matter?

Lower severity and a low EPSS score (1.44%). Track it; it rarely justifies an emergency change on its own.

Description

Low descenders on some Tibetan characters in several fonts on OS X are clipped when rendered in the addressbar. When used as part of an Internationalized Domain Name (IDN) this can be used for domain name spoofing attacks. Note: This attack only affects OS X operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 58.

CVSS 3.0
5.3 MEDIUMCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS
1.44% probability · 73th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-20
Affected
mozilla/firefox
Source
security@mozilla.org
EPSS trend
0%3%5%27 October 2026: 1.44%27 October 202627 October 2026

EPSS 1.4% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.