CVE-2026-91973

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.

  • Published Sep 15, 2026
  • CVSS 8.7 high
  • 0.7% chance of exploitation in the next 30 days (EPSS)
  • A fix is available

Affected software

CVE-2026-91973 at the National Vulnerability Database