GITHUB.COM/GETKIN/KIN-OPENAPI · CVE-2026-100353 · Package
FIX → 0.149.0
kin-openapi is a Go library for validating requests against OpenAPI specs. Three code paths in its openapi3filter package panic on nil items, and an earlier fix for the same class of panic was incomplete.
first public Aug 28, 2026 · 3 sources
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Services that import kin-openapi's openapi3filter package to validate incoming requests against an OpenAPI schema. A crash from a panic is most likely in a service that accepts untrusted request bodies. Projects that do not import openapi3filter, or that run only on versions outside the affected range, can skip it.
Not affected if openapi3filter-unused, version-outside-range
Who cares api-validation, cwe-476, go, kin-openapi, openapi
go list -m github.com/getkin/kin-openapi in the module and look for a version from 0.136.0 up to, but not including, 0.149.0.github.com/getkin/kin-openapi at those versions.Upgrade to 0.149.0
The fix for GHSA-p6wj-qrr4-pgh5 addressed a nil-pointer dereference that occurs when an OpenAPI 3.1 array schema omits the items keyword (which is legal under JSON Schema 2020-12). That fix patched three decoder paths: the standalone parseArray function, the top-level array check in UrlencodedBodyDecoder, and MultipartBodyDecoder.
Three additional crash paths were missed. All of them reach the unguarded urlValuesDecoder.parseArray method (openapi3filter/req_resp_decoder.go:576) or the unguarded array branch in buildResObj (line 1015):
type: array and no items.items.allOf / / sub-schema. This path bypasses the guard added by the GHSA-p6wj-qrr4-pgh5 fix, because that guard only inspects top-level properties.Are you affected?
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github.com/getkin/kin-openapi moves to 0.149.0.anyOfoneOfEach path is triggerable by an unauthenticated client and produces a deterministic nil-pointer panic during request validation.
The three paths patched for GHSA-p6wj-qrr4-pgh5 each received a nil-items guard:
// standalone parseArray (line 1143) -- GUARDED
func parseArray(raw []string, schemaRef *openapi3.SchemaRef) ([]any, error) {
if schemaRef.Value.Items == nil || schemaRef.Value.Items.Value == nil { ... }
// UrlencodedBodyDecoder top-level property loop (line 1441) -- GUARDED
if propSchema.Value.Items == nil || propSchema.Value.Items.Value == nil { ... }
// MultipartBodyDecoder (line 1587) -- GUARDED
if valueSchema.Value.Items == nil { ... }
But urlValuesDecoder.parseArray (line 576), which handles query-parameter and urlencoded-body array decoding, has no such guard:
func (d *urlValuesDecoder) parseArray(raw []string, schemaRef *openapi3.SchemaRef) ([]any, error) {
var value []any
for i, v := range raw {
item, err := d.parseValue(v, schemaRef.Value.Items) // Items is nil -> panic in parseValue
parseValue immediately dereferences the schema it is handed:
func (d *urlValuesDecoder) parseValue(v string, schema *openapi3.SchemaRef) (any, error) {
if len(schema.Value.AllOf) > 0 { // schema == nil here -> nil pointer dereference
For the deepObject path, buildResObj (line 1015) has the same gap. Its array branch recurses with schema.Value.Items (line 1028), which can be nil, and the recursive call dereferences it at line 1015:
case schema.Value.Type.Is("array"):
// ...
for i := range arr {
r, err := buildResObj(params, mapKeys, strconv.Itoa(i), schema.Value.Items) // nil Items
For the allOf body path, UrlencodedBodyDecoder validates only top-level schema.Value.Properties (line 1429-1449). But decodeSchemaConstructs (line 1474) recursively walks AllOf / AnyOf / OneOf sub-schemas and calls decodeProperty on their properties, which never pass through the top-level guard and reach urlValuesDecoder.parseArray.
v0.144.0, commit f0407d5)doc.Validate() first to prove the spec is legal, then drives openapi3filter.ValidateRequest directlySpec (query param ids is type: array, no items), request GET /test?ids=1&ids=2:
Validate() ACCEPTED the spec (type: array with no items is legal under OAS 3.1)
Calling ValidateRequest directly (no net/http recover)...
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x20 ...]
github.com/getkin/kin-openapi/openapi3filter.(*urlValuesDecoder).parseValue(...)
req_resp_decoder.go:605
github.com/getkin/kin-openapi/openapi3filter.(*urlValuesDecoder).parseArray(...)
req_resp_decoder.go:580
github.com/getkin/kin-openapi/openapi3filter.(*urlValuesDecoder).DecodeArray(...)
req_resp_decoder.go:569
...
github.com/getkin/kin-openapi/openapi3filter.ValidateRequest(...)
validate_request.go:83
exit status 2
Spec (deepObject param filter with array property tags, no items), request GET /test?filter[tags][0]=a:
Validate() ACCEPTED the spec
Calling ValidateRequest directly...
panic: runtime error: invalid memory address or nil pointer dereference
github.com/getkin/kin-openapi/openapi3filter.buildResObj(...)
req_resp_decoder.go:1012
github.com/getkin/kin-openapi/openapi3filter.buildResObj(...) <- recursive call with nil Items
req_resp_decoder.go:1028
github.com/getkin/kin-openapi/openapi3filter.makeObject(...)
req_resp_decoder.go:947
...
exit status 2
Spec (urlencoded body, allOf sub-schema with array property tags, no items), request POST /submit body tags=a&tags=b:
Validate() ACCEPTED the spec
Calling ValidateRequest directly...
panic: runtime error: invalid memory address or nil pointer dereference
github.com/getkin/kin-openapi/openapi3filter.(*urlValuesDecoder).parseValue(...)
req_resp_decoder.go:605
github.com/getkin/kin-openapi/openapi3filter.(*urlValuesDecoder).parseArray(...)
req_resp_decoder.go:580
github.com/getkin/kin-openapi/openapi3filter.(*urlValuesDecoder).DecodeArray(...)
req_resp_decoder.go:569
...
github.com/getkin/kin-openapi/openapi3filter.decodeProperty(...) <- reached via decodeSchemaConstructs (allOf walker)
req_resp_decoder.go:1519
exit status 2
The decodeProperty frame confirms the array was reached by walking the allOf sub-schema, bypassing the top-level guard that the GHSA-p6wj-qrr4-pgh5 fix added.
Adding a single nil-items guard to urlValuesDecoder.parseArray (plus one to the buildResObj array branch) turns all three panics into clean validation errors:
poc1: Returned normally, err = parameter "ids" in query has an error: array items schema is required for decoding
poc2: Returned normally, err = parameter "filter" in query has an error: path tags: array items schema is required
poc3: Returned normally, err = <nil> (no panic; the allOf property is skipped by the decoder)
This confirms urlValuesDecoder.parseArray is the shared root cause for Paths 1 and 3, and buildResObj for Path 2.
An unauthenticated client can trigger a deterministic nil-pointer panic in request validation with a single crafted request, against any application that validates OAS 3.1 requests with openapi3filter where a spec declares an array without items.
The severity depends on the host:
| Deployment | Behavior | Availability impact |
|---|---|---|
Standard net/http server (validation runs in the handler goroutine) | net/http recovers the panic per-connection; the connection is dropped and the process survives | Per-request denial of service (A:L) |
Non-net/http hosts (e.g. fasthttp/connect adapters) or validation performed in an application-spawned goroutine | The panic is not recovered; the process crashes | Full-process denial of service (A:H) |
This was verified in both configurations: under a live net/http server the process survived (the panic was logged as http: panic serving ... and the process exited 0 at end of test), while the direct-call PoCs above crashed the process with exit status 2.
This page as .md · .json · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Go Vulnerability Database, CC-BY 4.0 · NVD data is provided by NIST and is public domain · GitHub Advisory Database, CC-BY 4.0. Posts quoted belong to their authors.