CVE-2026-50197

### Summary `zalando/skipper`'s OpenPolicyAgent integration silently bypasses request-body inspection on HTTP/1.1 `Transfer-Encoding: chunked` and HTTP/2 requests that omit the `content-length` pseudo-header. When the `opaAuthorizeRequestWithBody` filter is configured, the `OpenPolicyAgentInstance.ExtractHttpBodyOptionally` helper produces an empty `raw_body` for any request whose `Content-Length` header is missing, while the underlying chunked body still flows through to the upstream service. Rego policies that gate on `input.parsed_body` (e.g. "deny when a forbidden field is present") evaluate against an empty document, treat the forbidden field as absent, and authorize the request. The upstream handler then receives the full attacker payload that the policy intended to block. ### Affected versions `github.com/zalando/skipper` versions `<= v0.26.8` (the latest release on 2026-05-26, current `master` `4eed47ff`). The vulnerable helper and gate have lived in `filters/openpolicyagent/openpolicyagent.go` since the buffered-body extractor was introduced; no released version contains the fix at the time of filing. ### Privilege required Unauthenticated network access to the skipper proxy listener. The threat model targets operators who place skipper in front of a private upstream and rely on `opaAuthorizeRequestWithBody` to enforce body-content checks (field allow/deny lists, payload schema gates, content-moderation flags, multi-tenant per-action authorization). Both HTTP/1.1 and HTTP/2 clients are affected; HTTP/2 traffic without a `content-length` pseudo-header is the dominant case because Go's `net/http` sets `http.Request.ContentLength = -1` for chunked HTTP/1.1 AND for HTTP/2 requests whose framing carries the body as DATA frames without an explicit length header. ### Root cause `filters/openpolicyagent/openpolicyagent.go:1242-1269` (HEAD `4eed47ff`): ```go func bodyUpperBound(contentLength, maxBodyBytes int64) int64 { if contentLength <= 0 { re