https://db.gcve.eu/rss/recent/all/10 Most recent entries from all 2026-10-12T04:22:53.344611+00:00 Vulnerability-Lookup info@gcve.eu python-feedgen Contains only the most 10 recent entries. https://db.gcve.eu/vuln/fkie_cve-2026-91973 fkie_cve-2026-91973 2026-10-12T04:22:53.420274+00:00

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.

 https://db.gcve.eu/vuln/ghsa-m469-88xx-8rx2 GHSA-m469-88xx-8rx2 — Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passw… 2026-10-12T04:22:53.420400+00:00

Affected: Go: code.vikunja.io/api

### Summary The `/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.

### Details `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).

TOTP-enabled accounts and bot users are correctly refused, so this targets password-only accounts.

### PoC (verified at runtime against v2.5.0) ``` POST /api/v1/login x25 wrong passwords -> 429 from attempt 2 (throttled) PROPFIND /dav/principals/{user}/ x60 wrong passwords -> 401 x60, 429 x0 GET /feeds/notifications.atom x30 wrong passwords -> 401 x30, 429 x0 PROPFIND /dav/... with correct password -> 207 (proves the 401s are real auth failures) ```

### Impact The anti-brute-force floor guarding `/login` is entirely absent on `/dav`, `/feeds`, and `/.well-known`, giving an u…