Kludex Starlette HTTP Request/Response Smuggling Vulnerability

Kludex Starlette contains a HTTP request/response smuggling vulnerability that could allow attackers to inject paths into the host part, prepending the actual path leading to issues such as authentication bypass when the authentication depends on the reconstructed URL’s path. This vulnerability could be chaned with CVE-2026-42271.

Added to CISA’s Known Exploited Vulnerabilities catalog on 2026-09-02. Required action per CISA: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset’s internet exposure and ensuring adherence to BOD 26-04 patching guidelines. Due date: 2026-09-16.

This is an auto-synced KEV catalog record pending a full 0dayNews write-up — see CISA’s KEV catalog and the NVD record linked above for primary sources.