Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth

Advisories

Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth

severity: high
date: 9/15/2026
Affecting: vikunja >= 0, < 2.6.0
CVE: CVE-2026-91973
CWE: CWE-307 Improper Restriction of Excessive Authentication Attempts
CVSS: 8.7
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
References: GitHub Security Advisory (GHSA-m469-88xx-8rx2)
Credit: JellowBeanz26
Description: Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection. Remote unauthenticated attackers can issue unbounded credential-guessing requests against /dav, /.well-known, and /feeds routes to bypass the instance's anti-brute-force controls and compromise password-only accounts.

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