CVE-2026-30246

### Summary Fiber cache middleware's default key generator uses only `c.Path()` and does not include the query string. As a result, requests like `/?id=1` and `/?id=2` can map to the same cache key and share the same cached response. This can cause response mix-up (cache poisoning-like behavior) for endpoints where response content depends on query parameters. ### Details Default configuration in cache middleware: - `KeyGenerator: func(c fiber.Ctx) string { return utils.CopyString(c.Path()) }` References: - https://github.com/gofiber/fiber/blob/main/middleware/cache/config.go#L90-L92 - https://github.com/gofiber/fiber/blob/main/middleware/cache/cache_test.go#L599-L621 The existing test demonstrates that when handler output depends on query parameter `id`, a second request with a different query still returns the first cached response (cache hit), confirming query is not part of the default cache key. ### PoC Minimal PoC: ```go package main import ( "log" "github.com/gofiber/fiber/v3" "github.com/gofiber/fiber/v3/middleware/cache" ) func main() { app := fiber.New() app.Use(cache.New()) // default config app.Get("/", func(c fiber.Ctx) error { return c.SendString(c.Query("id", "1")) }) log.Fatal(app.Listen(":3000")) } ``` Reproduction: 1. `GET /?id=1` - Cache miss - Response body: `1` 2. `GET /?id=2` - Cache hit - Response body: `1` (expected `2`) Local verification command used: ```bash go test ./middleware/cache -run Test_Cache_WithNoCacheRequestDirective -count=1 ``` Observed result: test passes, confirming this is current behavior. ### Impact - Responses that should vary by query parameters can be mixed between requests. - In real deployments, this may leak or corrupt user/tenant-specific content if query parameters influence context or data selection. - This is deployment-dependent but security-relevant, and not safe-by-default for query-variant responses. ### Suggested remediation - Change default cache key generation to include path + normalized query string (or canonicalized original URL). - Keep ability for custom key generators. - Add explicit documentation warning that path-only keying is unsafe for query-dependent responses.

Fiber: Cache middleware key generator ignores query string in github.com/gofiber/fiber