KMail since version 5.3.0 used a QWebEngine based viewer that had JavaScript enabled. Since the generated html is executed in the local file security context by default access to remote and local URLs was enabled.
Severity
CVSS 3.0
8.1 high
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
EPSS
1.9% chance of exploitation in the next 30 days; higher than 79% of CVEs (scores of 2026-10-31)