{"id":"CVE-2026-30246","aliases":["GHSA-35hp-hqmv-8qg8","GO-2026-5069"],"url":"https://o3.security/vulnerability/CVE-2026-30246","summary":"github.com/gofiber/fiber/v3 cache middleware can mix responses across 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.","published":"2026-05-05T12:40:19.813Z","modified":"2026-08-27T18:26:21.073016515Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"},"epss":{"score":0.00251,"percentile":0.16641,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/gofiber/fiber/v3","fixedVersion":"3.2.0"}],"fix":{"url":"https://github.com/gofiber/fiber/commit/050ff1ff18511c1475b8ec627460216aaecddd4e","label":"gofiber/fiber@050ff1f"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/30xxx/CVE-2026-30246.json"},{"type":"ADVISORY","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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T18:26:21.073016515Z"}}