CVE-2026-48710
Kludex Starlette HTTP Request/Response Smuggling Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 16 September 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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.
- CVSS 3.1
- 6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- EPSS
- 70.29% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 2 September 2026 · due 16 September 2026
- Weakness
- CWE-444, CWE-1289
- Affected
- encode/starlette · redhat/ai inference server · redhat/ansible automation platform · redhat/migration toolkit for applications · redhat/openshift ai · redhat/openshift lightspeed · redhat/satellite · redhat/enterprise linux ai
- Source
- security-advisories@github.com
EPSS moved from 7.1% on 24 September 2026 to 70.3% on 29 October 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
CISA notes
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. This vulnerability affects an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-48710
References
- https://badhost.orgMitigation, Third Party Advisory
- https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6Patch
- https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mrVendor Advisory
- https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yamlThird Party Advisory
- https://ostif.org/disclosing-the-badhost-vulnerability-in-starletteMitigation, Third Party Advisory
- https://www.secwest.net/starletteExploit, Mitigation, Third Party Advisory
- https://www.x41-dsec.de/lab/advisories/x41-2026-002-starletteExploit, Mitigation, Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:22992Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:22993Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:23346Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:24866Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:26226Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:30088Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:30089Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:34456Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:34526Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:34532Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:37275Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:43038Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:44696Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:51357Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:60520Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:63337Third Party Advisory
- https://access.redhat.com/security/cve/CVE-2026-48710Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2481742Issue Tracking, Third Party Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48710.jsonThird Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48710Third Party Advisory, US Government Resource
- https://www.wiz.io/blog/ai-infrastructure-honeypotExploit, Third Party Advisory
- https:/www.microsoft.com/en-us/security/blog/2026/08/26/when-ai-infrastructure-becomes-target-securing-gateways-control-pointsBroken Link
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.