CVE-2026-77354

### Summary An uncontrolled resource consumption vulnerability in `openapi3filter` lets any unauthenticated client force multi-gigabyte heap allocation with a single, tiny HTTP request. When a spec declares a `deepObject`-style query parameter whose schema contains an array (a normal, documented pattern), the decoder reconstructs the array by reading the **largest attacker-supplied index** and allocating one slot for every position from `0` up to that index — *before* schema validation (including `maxItems`) ever runs. A request as small as 24 bytes (`?param[items][50000000]=x`) drives heap allocation to **~6.1 GiB**, reliably triggering an OOM kill / restart loop on memory-constrained services. ### Details The OpenAPI `style: deepObject` serialization lets clients express arrays in the query string using bracket notation, e.g. `param[items][0]=a&param[items][1]=b`. The decoder first collects these into an intermediate `map[string]any` keyed by the string of the index, then converts that sparse map into a real `[]any` in [`sliceMapToSlice`](https://github.com/getkin/kin-openapi/blob/master/openapi3filter/req_resp_decoder.go#L936): ```go // req_resp_decoder.go (vulnerable version) func sliceMapToSlice(m map[string]any) ([]any, error) { var result []any keys := make([]int, 0, len(m)) for k := range m { key, err := strconv.Atoi(k) // "50000000" -> 50000000, attacker-controlled if err != nil { return nil, fmt.Errorf("array indexes must be integers: %w", err) } keys = append(keys, key) } max := -1 for _, k := range keys { if k > max { max = k // max = attacker's index, unbounded } } for i := 0; i <= max; i++ { // <-- unbounded loop, 0 .. max val, ok := m[strconv.Itoa(i)] if !ok { result = append(result, nil) // fills every sparse hole with nil continue } result = append(result, val) } return result, nil } ``` A second, equally-sized allocation follows immediately in [`buildR