CVE-2026-48710: Starlette auth bypass via malformed Host header

CVE-2026-48710 · Severity: critical · CVSS 6.5 · Exploited in the wild · Published 2026-05-26

Kludex Starlette, a popular Python web framework library, contains a HTTP request/response smuggling vulnerability that allows attackers to manipulate HTTP headers and inject malicious path information. By exploiting this flaw, an attacker can bypass authentication mechanisms that rely on URL path validation, potentially gaining unauthorized access to protected resources or performing actions on behalf of authenticated users.

Technologies: Kludex Starlette, starlette (PyPI). Vendors: Kludex, PyPI.

Quick answers

Is CVE-2026-48710 exploited in the wild?
Yes. CVE-2026-48710 is known to be exploited in the wild, first recorded on 2 September 2026. Treat it as urgent.
How severe is CVE-2026-48710?
Critical severity, with a CVSS score of 6.5, published 26 May 2026.
Which products and versions are affected?
Kludex Starlette < 1.0.1; Kludex Starlette-Context <= 1.0.0; starlette (PyPI) ECOSYSTEM:introduced=0,fixed=1.0.1.
Is there a fix for CVE-2026-48710?
Yes. starlette (PyPI): upgrade to 1.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-48710 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-48710?
Check whether you run Kludex Starlette, Kludex Starlette-Context or starlette (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • starlette (PyPI): upgrade to 1.0.1 or later
    pip install "starlette>=1.0.1"

Technical details

This is a HTTP request/response smuggling vulnerability in Kludex Starlette that arises from improper handling of HTTP headers when reconstructing request paths and URLs. The vulnerability allows an attacker to inject malicious path information into the host header portion of an HTTP request, causing the server to misinterpret the request path. Since authentication decisions may be based on the reconstructed URL path, an attacker can craft requests that bypass path-based authentication checks. The attack vector is network-based and requires no authentication or special privileges. The vulnerability has been observed in active exploitation in the wild. A patch or mitigation is recommended, and this issue may compound with CVE-2026-42271 for more severe impacts.

Affected products

  • Kludex Starlette

Identifiers

  • CVE-2026-48710
  • GHSA-86qp-5c8j-p5mr
  • PYSEC-2026-161

Timeline

  • 2026-09-02: disclosed
  • exploited: Confirmed exploitation in the wild

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