{"id":"EUVD-2026-78649","revision":null,"records":[{"revision":"edecf39170b24f549073a290a2c8ba6b","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-91973","aliases":[],"title":"Vikunja before 2.6.0 Authentication Bypass via CalDAV BasicAuth","description":"Vikunja before 2.6.0 contains an authentication bypass vulnerability in CalDAV BasicAuth endpoints that lack rate limiting protection. 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Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-91973","identifiers":["CVE-2026-91973"]},"retained":false,"historicalAffected":[]},{"revision":"7eb978075c794b05aff64110ad4b42be","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-m469-88xx-8rx2","aliases":["CVE-2026-91973","GO-2026-6737"],"title":"Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords","description":"### Summary\nThe `/dav`, `/.well-known`, and `/feeds` groups are registered on the root Echo instance with only BasicAuth and no rate limiter. CalDAV BasicAuth accepts the plain account password, so password guessing over `/dav` is unbounded and never returns 429, while `/api/v1/login` is throttled from the tenth attempt. The only anti-brute-force control on the instance is therefore bypassable.\n\n### Details\n`pkg/routes/routes.go` (~lines 238-249) registers `/.well-known`, `/dav`, and `/feeds` with `middleware.BasicAuth(...)` and nothing else; `registerCalDavRoutes` adds no limiter. `pkg/routes/caldav/auth.go` (~lines 88-93) falls through to `user.CheckUserCredentials` with the plain account password when no CalDAV token matches. In contrast, `/register`, `/login`, etc. are wrapped by `unauthRateLimit()` — an unconditional 10/min/IP pre-auth floor that ignores `ratelimit.enabled` (default false).\n\nTOTP-enabled accounts and bot users are correctly refused, so this targets password-only accounts.\n\n### PoC (verified at runtime against v2.5.0)\n```\nPOST /api/v1/login  x25 wrong passwords  -> 429 from attempt 2 (throttled)\nPROPFIND /dav/principals/{user}/  x60 wrong passwords  -> 401 x60, 429 x0\nGET /feeds/notifications.atom  x30 wrong passwords  -> 401 x30, 429 x0\nPROPFIND /dav/... with correct password -> 207 (proves the 401s are real auth failures)\n```\n\n### Impact\nThe anti-brute-force floor guarding `/login` is entirely absent on `/dav`, `/feeds`, and `/.well-known`, giving an unbounded credential-guessing surface against account passwords. (bcrypt caps throughput to a few guesses/second, but nothing caps the number of attempts.) Reported as an authentication-control bypass, not a DoS.\n\n### Fix\nApply the unconditional pre-auth rate-limit floor to the `/dav`, `/.well-known`, and `/feeds` groups.","state":0,"publishedAt":"2026-10-09T20:52:04+00:00","modifiedAt":"2026-10-19T21:40:52.6043176+00:00","affected":[{"ecosystem":"Go","name":"code.vikunja.io/api","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"2.6.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2","https://nvd.nist.gov/vuln/detail/CVE-2026-91973","https://github.com/go-vikunja/vikunja/pull/3688","https://github.com/go-vikunja/vikunja","https://github.com/go-vikunja/vikunja/releases/tag/v2.6.0","https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth"],"sourceUrl":"https://github.com/advisories/GHSA-m469-88xx-8rx2","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-m469-88xx-8rx2","identifiers":["GHSA-m469-88xx-8rx2","CVE-2026-91973","GO-2026-6737"]},"retained":false,"historicalAffected":[]},{"revision":"b0d7378e036f4f3cbf52808d829576ad","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-p2vv-wrh8-x466","aliases":[],"title":"Duplicate Advisory: Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords","description":"### Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-m469-88xx-8rx2. This link is maintained to preserve external references.\n\n### Original Description\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.","state":2,"publishedAt":"2026-09-15T18:32:30+00:00","modifiedAt":"2026-10-09T21:00:06.9806848+00:00","affected":[{"ecosystem":"Go","name":"code.vikunja.io/api","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"last_affected","version":"2.5.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","score":null,"severity":null},{"system":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2","https://nvd.nist.gov/vuln/detail/CVE-2026-91973","https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth"],"sourceUrl":"https://github.com/advisories/GHSA-p2vv-wrh8-x466","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-p2vv-wrh8-x466","identifiers":["GHSA-p2vv-wrh8-x466"]},"retained":false,"historicalAffected":[]},{"revision":"e53251a72ec5435588ec2782ae4e3928","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GO-2026-6737","aliases":["CVE-2026-91973","GHSA-m469-88xx-8rx2"],"title":"Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords in code.vikunja.io/api","description":"Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords in code.vikunja.io/api.\n\nNOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.\n\n(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)\n\nThe additional affected modules and versions are: code.vikunja.io/api before v2.6.0.","state":0,"publishedAt":"2026-10-19T21:08:26+00:00","modifiedAt":"2026-10-19T21:31:35.964762+00:00","affected":[{"ecosystem":"Go","name":"code.vikunja.io/api","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://github.com/go-vikunja/vikunja/security/advisories/GHSA-m469-88xx-8rx2","https://nvd.nist.gov/vuln/detail/CVE-2026-91973","https://github.com/go-vikunja/vikunja/pull/3688","https://github.com/go-vikunja/vikunja/releases/tag/v2.6.0","https://www.vulncheck.com/advisories/vikunja-before-2.6.0-authentication-bypass-via-caldav-basicauth"],"sourceUrl":"https://osv.dev/vulnerability/GO-2026-6737","license":"OSV · upstream source license applies","key":"osv:GO-2026-6737","identifiers":["GO-2026-6737","CVE-2026-91973","GHSA-m469-88xx-8rx2"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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