Intelligence online17 sources monitored8 actively exploited 7d26 published 24hChecked recently
Vulnerability record

CVE-2026-48710

Kludex Starlette HTTP Request/Response Smuggling Vulnerability

ElevatedExploitation confirmedCISA KEV
What should I do?

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run Starlette, fix it now.

CISA required action: 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.

US federal civilian agencies must remediate by Sep 16, 2026.

Patch status

Official fix available since

Apply the vendor's update to every affected system. Check the fixed-in versions below where known.

Basis: NVD patch reference

Description

Starlette is a lightweight ASGI framework/toolkit. Prior to version 1.0.1, the HTTP `Host` request header was not validated before being used to reconstruct `request.url`. Because the routing algorithm relies on the raw HTTP path while `request.url` is rebuilt from the `Host` header, a malformed header could make `request.url.path` differ from the path that was actually requested. Middleware and endpoints that apply security restrictions based on `request.url` (rather than the raw `scope` path) could therefore be bypassed. Users should upgrade to a version greater than or equal to version 1.0.1, which validates the `Host` header against the grammar of RFC 9112 §3.2 / RFC 3986 §3.2.2 when constructing `request.url` and falls back to `scope["server"]` for malformed values.

Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.

Affected products

ProductVendorSource
StarletteKludexKEV

Sources: KEV = CISA Known Exploited Vulnerabilities catalog. Version details have not been published yet.

Intelligence timeline

Developments from the last 30 days, newest first.

No developments recorded for CVE-2026-48710 in the last 30 days.

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Coverage

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References