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Security Issue in Kludex Starlette Could Let Attackers Bypass Website Protections

A security weakness has been found in the Kludex Starlette software that could allow attackers to bypass some website security checks. This is important because it is actively being exploited and affects software used in web applications. Small organisations using this software should take action to protect themselves.

04 September 2026

Reference: CVE-2026-48710

1. What is being reported?

The Kludex Starlette software did not properly check the 'Host' part of incoming web requests before using it to build website addresses. This flaw means attackers can send specially crafted requests that trick the system into ignoring security rules, potentially allowing unauthorised access.

2. What this means in plain English

If your organisation uses Kludex Starlette in your website or web applications, attackers might be able to get around security controls. This could lead to unauthorised access or other security issues. It is important to fix this to keep your systems safe.

3. Could this affect a small business?

Small businesses or charities using Kludex Starlette in their websites or online services could be affected. If you do not use this software, or it is not part of your web systems, this vulnerability likely does not affect you.

4. What to do now

  • Check if your website or web applications use Kludex Starlette software.
  • Ask your IT provider or software supplier if your version is older than 1.0.1 and needs updating.
  • Apply the update to version 1.0.1 or later as soon as possible to fix the issue.
  • If you use cloud services with this software, ensure they follow security update guidance or consider discontinuing use if no fix is available.

5. Ask your IT provider

Can you confirm if our systems use Kludex Starlette, and if so, have we updated to version 1.0.1 or later to address the known security vulnerability CVE-2026-48710?

6. Bottom line

Update Kludex Starlette software promptly to prevent attackers from bypassing your website's security controls.

Information based on CISA KEV, NVD and reputable security reporting.

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