High (7.5). EPSS 2.1% chance of exploitation in the next 30 days.
The CentralNotice extension for MediaWiki before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 sets the Cache-Control header to cache session cookies when a user is autocreated, which allows remote attackers to authenticate as the created user.
Severity
CVSS 3.1
7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
2.1% chance of exploitation in the next 30 days; higher than 82% of CVEs (scores of 2026-10-31)