Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords

{
  "id": "5eb52f2a09c787a94424186da6aaa3934ef6a23d7e72619c5d64614859ce315e",
  "url": "https://osv.dev/vulnerability/GHSA-m469-88xx-8rx2",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Vikunja: CalDAV and feeds BasicAuth endpoints have no rate limit, bypassing the anti-brute-force floor on account passwords",
    "summary": "### 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 unbounded cr",
    "evidence": "osv:GHSA-m469-88xx-8rx2",
    "products": [
      {
        "name": {
          "value": "code.vikunja.io/api",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.6.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "GHSA-m469-88xx-8rx2",
      "aliases": [
        "CVE-2026-91973",
        "GHSA-m469-88xx-8rx2",
        "GO-2026-6737"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.6.0"
                }
              ]
            }
          ],
          "package": {
            "name": "code.vikunja.io/api",
            "purl": "pkg:golang/code.vikunja.io/api",
            "ecosystem": "Go"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-m469-88xx-8rx2/GHSA-m469-88xx-8rx2.json",
            "last_known_affected_version_range": "<= 2.5.0"
          }
        }
      ],
      "modified": "2026-10-19T21:40:52.604317649Z",
      "provider": "osv",
      "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"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-307"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": null,
        "github_reviewed_at": "2026-10-09T20:52:04Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-91973",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 376747,
  "published_at": "2026-10-09T20:52:04+00:00"
}