{"cve":"CVE-2026-91973","nvd":{"published":"2026-09-15T16:17:54.230","modified":"2026-09-16T20:16:09.343","status":"Deferred","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.","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","score":8.7},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","score":7.5},"cwes":["CWE-307"],"references":["https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2","https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth","https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:53:43.293028046+00:00"},"epss":{"cve":"CVE-2026-91973","score":0.00672,"percentile":0.52096,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-m469-88xx-8rx2","url":"https://osv.dev/vulnerability/GHSA-m469-88xx-8rx2","summary":"Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords","modified":"2026-10-19T21:40:52.604317649Z","packages":[{"ecosystem":"Go","name":"code.vikunja.io/api","purl":"pkg:golang/code.vikunja.io/api","ranges":["<2.6.0"],"fixed":["2.6.0"]}]},{"id":"GO-2026-6737","url":"https://osv.dev/vulnerability/GO-2026-6737","summary":"Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords in code.vikunja.io/api","modified":"2026-10-19T21:31:35.964761967Z","packages":[{"ecosystem":"Go","name":"code.vikunja.io/api","purl":"pkg:golang/code.vikunja.io/api","ranges":["all versions"],"fixed":[]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}