{"id":"CVE-2026-91973","title":"Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection","summary":"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…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","cwe":["CWE-307"],"vendor":"go-vikunja","product":"vikunja","affected":["vikunja < 2.6.0"],"published":"2026-09-15","updated":"2026-09-16","sourceUpdated":"2026-09-16T20:16:09.343","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-91973","references":[{"url":"https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth","label":"disclosure@vulncheck.com"},{"url":"https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd","cve.org","exploit-available"],"exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-15T15:53:33.159049Z"},"ingestedAt":"2026-09-15T15:39:12.913Z","epss":0.00609,"epssPercentile":0.47529,"slug":"CVE-2026-91973","body":"## Overview\n\nVikunja 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":53,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":204286,"id":"CVE-2026-91973","ts":1789490446627,"field":"exploit_available","old":"false","new":"true"}]}