CVE-2026-65838: Skipper: an oversized declared-`Content-Length` body still hands OPA an empty `parsed_body`, so deny-on-presence Rego policies fail OPEN while the full payload reaches upstream
Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.27.35, the opaAuthorizeRequestWithBody filter in filters/openpolicyagent/openpolicyagent.go can allow an oversized declared Content-Length request to bypass a deny-on-presence Rego policy because ExtractHttpBodyOptionally leaves OPA with an empty parsedbody while forwarding the complete request body upstream. This incomplete remediation of CVE-2026-50197 affects deployments that authorize request-body content and exceed -open-policy-agent-max-request-body-size, which defaults to 1 MB. Policy logic that does not reject input.attributes.request.http.truncatedbody can therefore fail open and permit a forbidden payload to reach the protected service, while small bodies and the previously fixed chunked-body case are evaluated normally. This issue is fixed in version 0.27.35.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
open-policy-agentto a version that resolves this vulnerability.Fixed in 0.27.35
Event History
Frequently Asked Questions
Which deployments are exposed to this bypass?
Deployments using Skipper's opaAuthorizeRequestWithBody filter to authorize request-body content are affected if requests can exceed -open-policy-agent-max-request-body-size, which defaults to 1 MB. The vulnerable behavior applies before version 0.27.35.
What must an attacker send to bypass the policy?
An attacker needs to send a request with an oversized declared Content-Length body. If the Rego policy relies on the presence of body content and does not reject input.attributes.request.http.truncated_body, OPA receives an empty parsed_body while the complete payload is forwarded upstream.
Are all request bodies evaluated incorrectly?
No. Small bodies are evaluated normally, and the previously fixed chunked-body case is also evaluated normally. This issue concerns oversized requests with a declared Content-Length.
What can be done if upgrading is not immediately possible?
Ensure Rego policy logic rejects input.attributes.request.http.truncated_body rather than treating an empty parsed_body as evidence that forbidden content is absent. Reducing or enforcing request-body limits may also prevent oversized bodies from reaching the affected authorization path.
How can I determine whether a request may have bypassed authorization?
Review whether the request used a declared Content-Length larger than the configured -open-policy-agent-max-request-body-size and whether the applicable policy depended on parsed_body presence without rejecting truncated_body. Under those conditions, the upstream service may have received the full body even though OPA evaluated an empty parsed_body.