CVE-2026-30246: Github.com/gofiber/fiber/v3 Fiber's Cache Middleware Default Key Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-35hp-hqmv-8qg8",
  "modified" : "2026-05-08T13:42:45Z",
  "published" : "2026-04-28T22:28:14Z",
  "aliases" : [ "CVE-2026-30246" ],
  "summary" : "Fiber's cache middleware default key generator ignores query string, causing response mix-up across distinct query parameters",
  "details" : "### Summary\nFiber cache middleware's default key generator uses only `c.Path()` and does not include the query string.\nAs a result, requests like `/?id=1` and `/?id=2` can map to the same cache key and share the same cached response.\n\nThis can cause response mix-up (cache poisoning-like behavior) for endpoints where response content depends on query parameters.\n\n### Details\nDefault configuration in cache middleware:\n\n- `KeyGenerator: func(c fiber.Ctx) string { return utils.CopyString(c.Path()) }`\n\nReferences:\n- https://github.com/gofiber/fiber/blob/main/middleware/cache/config.go#L90-L92\n- https://github.com/gofiber/fiber/blob/main/middleware/cache/cache_test.go#L599-L621\n\nThe 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.\n\n### PoC\nMinimal PoC:\n\n```go\npackage main\n\nimport (\n    \"log\"\n\n    \"github.com/gofiber/fiber/v3\"\n    \"github.com/gofiber/fiber/v3/middleware/cache\"\n)\n\nfunc main() {\n    app := fiber.New()\n    app.Use(cache.New()) // default config\n\n    app.Get(\"/\", func(c fiber.Ctx) error {\n        return c.SendString(c.Query(\"id\", \"1\"))\n    })\n\n    log.Fatal(app.Listen(\":3000\"))\n}\n```\n\nReproduction:\n\n1. `GET /?id=1`\n   - Cache miss\n   - Response body: `1`\n2. `GET /?id=2`\n   - Cache hit\n   - Response body: `1` (expected `2`)\n\nLocal verification command used:\n\n```bash\ngo test ./middleware/cache -run Test_Cache_WithNoCacheRequestDirective -count=1\n```\n\nObserved result: test passes, confirming this is current behavior.\n\n### Impact\n- Responses that should vary by query parameters can be mixed between requests.\n- In real deployments, this may leak or corrupt user/tenant-specific content if query parameters influence context or data selection.\n- This is deployment-dependent but security-relevant, and not safe-by-default for query-variant responses.\n\n### Suggested remediation\n- Change default cache key generation to include path + normalized query string (or canonicalized original URL).\n- Keep ability for custom key generators.\n- Add explicit documentation warning that path-only keying is unsafe for query-dependent responses.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/gofiber/fiber/v3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.2.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.1.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/gofiber/fiber/security/advisories/GHSA-35hp-hqmv-8qg8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-30246"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gofiber/fiber/commit/050ff1ff18511c1475b8ec627460216aaecddd4e"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gofiber/fiber/commit/9a0d12c07ed895b84c72987f9288b04137afe5de"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/gofiber/fiber"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gofiber/fiber/blob/main/middleware/cache/cache_test.go#L599-L621"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gofiber/fiber/blob/main/middleware/cache/config.go#L90-L92"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-436", "CWE-524" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-28T22:28:14Z",
    "nvd_published_at" : "2026-05-05T13:16:28Z"
  }
}