Kimai before 2.54.0 contains a timing oracle vulnerability in TokenAuthenticator that allows unauthenticated attackers to enumerate valid usernames via X-AUTH-USER header. Attackers can measure response time differences when the password hasher runs only for existing users, enabling username enumeration with no login throttling protection.
https://www.vulncheck.com/advisories/kimai-before-2.54.0-username-enumeration-via-timing-oracle
https://github.com/kimai/kimai/security/advisories/GHSA-jrc6-fmhw-fpq2
Published: 2026-08-25
Base Score: 2.6
Vector: CVSS2#AV:N/AC:H/Au:N/C:P/I:N/A:N
Severity: Low
Base Score: 3.7
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Severity: Low
Base Score: 6.3
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Severity: Medium