CVE-2024-37298: Github.com/gorilla/schema Potential Memory Exhaustion Attack Due Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3669-72x9-r9p3",
  "modified" : "2024-07-05T21:29:07Z",
  "published" : "2024-07-01T20:35:12Z",
  "aliases" : [ "CVE-2024-37298" ],
  "summary" : "Potential memory exhaustion attack due to sparse slice deserialization",
  "details" : "### Details\n\nRunning `schema.Decoder.Decode()` on a struct that has a field of type `[]struct{...}` opens it up to malicious attacks regarding memory allocations, taking advantage of the sparse slice functionality. For instance, in the Proof of Concept written below, someone can specify to set a field of the billionth element and it will allocate all other elements before it in the slice. \n\nIn the local environment environment for my project, I was able to call an endpoint like `/innocent_endpoint?arr.10000000.X=1` and freeze my system from the memory allocation while parsing `r.Form`. I think [this line](https://github.com/gorilla/schema/blob/main/decoder.go#L223) is responsible for allocating the slice, although I haven't tested to make sure, so it's just an educated guess.\n\n### Proof of Concept\n\nThe following proof of concept works on both v1.2.0 and v1.2.1. I have not tested earlier versions.\n\n```go\npackage main\n\nimport (\n\t\"fmt\"\n\n\t\"github.com/gorilla/schema\"\n)\n\nfunc main() {\n\tdec := schema.NewDecoder()\n\tvar result struct {\n\t\tArr []struct{ Val int }\n\t}\n\tif err := dec.Decode(&result, map[string][]string{\"arr.1000000000.Val\": {\"1\"}}); err != nil {\n\t\tpanic(err)\n\t}\n\tfmt.Printf(\"%#+v\\n\", result)\n}\n\n```\n\n### Impact\n\nAny use of `schema.Decoder.Decode()` on a struct with arrays of other structs could be vulnerable to this memory exhaustion vulnerability. There seems to be no possible solution that a developer using this library can do to disable this behaviour without fixing it in this project, so all uses of Decode that fall under this umbrella are affected. A fix that doesn't require a major change may also be harder to find, since it could break compatibility with some other intended use-cases.\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/gorilla/schema"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/gorilla/schema/security/advisories/GHSA-3669-72x9-r9p3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-37298"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gorilla/schema/commit/cd59f2f12cbdfa9c06aa63e425d1fe4a806967ff"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/gorilla/schema"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/gorilla/schema/blob/main/decoder.go#L223"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-07-01T20:35:12Z",
    "nvd_published_at" : "2024-07-01T19:15:04Z"
  }
}