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Vulnerabilities
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CVE-2026-6253

Updated on 13 May 2026

Severity

5.9 Medium severity

Details

CVSS score
5.9
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE ID
Links
NISTCIRCLRHELUbuntu

Overview

About vulnerability

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

Details

Affected product:
AlmaLinux 9.2 ESU , Alpine Linux 3.18 ELS , Amazon Linux 2 ELS , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Debian 10 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
Affected packages:
curl @ 8.12.1 (+16 more)

Fixes