Vikunja is an open-source self-hosted task management platform. Starting in version 0.8 and prior to version 2.2.0, unauthenticated users are able to bypass the application's built-in rate-limits by spoofing the `X-Forwarded-For` or `X-Real-IP` headers due to the rate-limit relying on the value of `(echo.Context).RealIP`. Unauthenticated users can abuse endpoints available to them for different potential impacts. The immediate concern would be brute-forcing usernames or specific accounts' passwords. This bypass allows unlimited requests against unauthenticated endpoints. Version 2.2.0 patches the issue.

Affected: Go: code.vikunja.io/api

### Summary Unauthenticated users are able to bypass the application's built-in rate-limits by spoofing the `X-Forwarded-For` or `X-Real-IP` headers due to the rate-limit relying on the value of `(echo.Context).RealIP`.

### Details In the first file below, the rate-limit for unauthenticated users can be observed being populated with the `ip` value. In the second file, it shows it using the `c.RealIP()` function for the `ip` case. Due to this, the rate-limit will rely on the value of one of the two mentioned headers (`X-Forwarded-For` or `X-Real-IP`). These can be spoofed by users client-side in order to completely bypass any unauthenticated rate-limits in place.

Some reverse proxies like Traefik will overwrite this value by default, but others will not, leaving any deployment that either isn't using a reserve proxy that specifically overwrites the header's value or isn't using a reverse proxy vulnerable.

**File 1:** pkg\routes\routes.go:318 ```go // This is the group with no auth // It is its own group to be able to rate limit this based on different heuristics n := a.Group("") setupRateLimit(n, "ip")

// Docs n.GET("/docs.json", apiv1.DocsJSON) n.GET("/docs", apiv1.RedocUI)

// Prometheus endpoint setupMetrics(n)

// Separate route for unauthenticated routes to enable rate limits for it ur := a.Group("") rate := limiter.Rate{ Period: 60 * time.Second, Limit: config.RateLimitNoAuthRoutesLimit.GetInt64(), } rateLimiter := createRateLimiter(rate) ur.Use…