CVE-2026-91972

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Summary

registerAPIRoutesV2 never applies the unconditional pre-auth rate-limit floor (unauthRateLimit()) to the v2 public routes — it passes that limiter only to /api/v2/ws — and otherwise relies on setupRateLimit, which registers nothing when ratelimit.enabled is false (the default). So on a stock install every v2 pre-auth endpoint (login, register, password-reset token, oauth token) is unthrottled, while its v1 twin is throttled.

Details

unauthRateLimit() -> perMinuteIPRateLimit("noauth", RateLimitNoAuthRoutesLimit) (pkg/routes/rate_limit.go, ~lines 100-118) is an unconditional per-IP floor (default 10/60s) that deliberately ignores RateLimitEnabled, which is why v1's pre-auth routes are throttled even with the global limiter off. v1 applies it: ur := a.Group(""); ur.Use(unauthRateLimit()) (pkg/routes/routes.go ~line 459). registerAPIRoutesV2 (~lines 405-431) passes the unauthRateLimit() instance only to /api/v2/ws; its auth routes get only setupRateLimit(a, ...), which is config-gated and registers nothing by default.

PoC (verified at runtime against v2.5.0)

POST /api/v1/login              x25 -> 429 from attempt 5
POST /api/v2/login              x25 -> 403 x25, 429 x0
POST /api/v1/user/password/token     -> 429 (throttled)
POST /api/v2/user/password/token x20 -> 404 x20, 429 x0

Request bodies are byte-identical across versions (shared user.Login / user.PasswordTokenRequest). Both v2 endpoints reach their handlers (403/404, not route-404), so the comparison is valid.

Impact

The pre-auth rate-limit floor — the instance's only default anti-brute-force / anti-abuse control — is absent on all v2 public endpoints. Enables unbounded credential guessing, account-enumeration probing, and password-reset flooding on a default install. Reported as an authentication-control bypass, not a DoS.

Fix

Apply unauthRateLimit() to the v2 public route group, matching v1.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-6rvj-qwjf-3m4q. This link is maintained to preserve external references.

Original Description

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Summary

registerAPIRoutesV2 never applies the unconditional pre-auth rate-limit floor (unauthRateLimit()) to the v2 public routes — it passes that limiter only to /api/v2/ws — and otherwise relies on setupRateLimit, which registers nothing when ratelimit.enabled is false (the default). So on a stock install every v2 pre-auth endpoint (login, register, password-reset token, oauth token) is unthrottled, while its v1 twin is throttled.

Details

unauthRateLimit() -> perMinuteIPRateLimit("noauth", RateLimitNoAuthRoutesLimit) (pkg/routes/rate_limit.go, ~lines 100-118) is an unconditional per-IP floor (default 10/60s) that deliberately ignores RateLimitEnabled, which is why v1's pre-auth routes are throttled even with the global limiter off. v1 applies it: ur := a.Group(""); ur.Use(unauthRateLimit()) (pkg/routes/routes.go ~line 459). registerAPIRoutesV2 (~lines 405-431) passes the unauthRateLimit() instance only to /api/v2/ws; its auth routes get only setupRateLimit(a, ...), which is config-gated and registers nothing by default.

PoC (verified at runtime against v2.5.0)

POST /api/v1/login              x25 -> 429 from attempt 5
POST /api/v2/login              x25 -> 403 x25, 429 x0
POST /api/v1/user/password/token     -> 429 (throttled)
POST /api/v2/user/password/token x20 -> 404 x20, 429 x0

Request bodies are byte-identical across versions (shared user.Login / user.PasswordTokenRequest). Both v2 endpoints reach their handlers (403/404, not route-404), so the comparison is valid.

Impact

The pre-auth rate-limit floor — the instance's only default anti-brute-force / anti-abuse control — is absent on all v2 public endpoints. Enables unbounded credential guessing, account-enumeration probing, and password-reset flooding on a default install. Reported as an authentication-control bypass, not a DoS.

Fix

Apply unauthRateLimit() to the v2 public route group, matching v1.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-6rvj-qwjf-3m4q. This link is maintained to preserve external references.

Original Description

Vikunja versions before 2.6.0 fail to apply rate limiting to /api/v2 public authentication endpoints including login, register, password-reset, and OAuth token routes. Remote unauthenticated attackers can perform unbounded credential guessing, account enumeration, and password-reset flooding attacks without throttling restrictions.

Vikunja: Every /api/v2 pre-auth endpoint is unthrottled on a stock install while its /api/v1 twin is rate limited in code.vikunja.io/api.

NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.

(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)

The additional affected modules and versions are: code.vikunja.io/api before v2.6.0.