CVE intelligence

CVE-2026-6253

Vulnerability intelligence

Published May 13, 2026Sources checked Nov 11, 2026

5.9MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-6253 and is rated Medium severity with a CVSS score of 5.9. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Jun 15, 2026

CBL-Mariner Releases

Vendor-listed releases

3.30.3-14
8.11.1-8

CISA KEVNot listedBased on the latest collected catalog

EPSS0.7%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-6253?

curl might erroneously pass on credentials for a first proxy to a second proxy.

This can happen when the following conditions are true:

1. curl is setup to use specific different proxies for different URL schemes 2. the first proxy needs credentials 3. the second proxy uses no credentials 4. while using the first proxy (using say `http://`), curl is asked to follow a redirect to a URL using another scheme (say `https://`), accessed using a second, different, proxy

Source: NVD