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OpenAdvisories
Medium · 5.9 CVE-2026-6253 EUVD-2026-29927

proxy credentials leak over redirect-to proxy

Published May 13, 2026 · Updated Sep 15, 2026 · Assigned by curl

Vendor: curl Product: curl Package: cmake Package: curl Package: curl Package: curl Package: curl Ecosystem: Alpine Ecosystem: Azure Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

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

Affected products

VendorProductAffectedFixed
curl curl 7.14.1 – < 8.14.2, 8.15.0 – < 8.16.1, 8.17.0 – < 8.20.0, 8.19.0, 8.18.0, 8.17.0, 8.16.0, 8.15.0, 8.14.1, 8.14.0, 8.13.0, 8.12.1, 8.12.0, 8.11.1, 8.11.0, 8.10.1, 8.10.0, 8.9.1, 8.9.0, 8.8.0, 8.7.1, 8.7.0, 8.6.0, 8.5.0, 8.4.0, 8.3.0, 8.2.1, 8.2.0, 8.1.2, 8.1.1, 8.1.0, 8.0.1, 8.0.0, 7.88.1, 7.88.0, 7.… 8.14.2

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Debian

Security tracker ↗
ReleasePackageFixed inAdvisory
Debian 14 curl 8.20.0~rc3-1 —
Debian 13 curl 8.14.1-2+deb13u4 —
Debian 12 curl No fix yet —

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu 26.04 LTS curl 8.18.0-1ubuntu2.1 —
Ubuntu 25.10 curl 8.14.1-2ubuntu1.3 —
Ubuntu 24.04 LTS curl 8.5.0-2ubuntu10.9 —
Ubuntu 22.04 LTS curl 7.81.0-1ubuntu1.24 —
Show 4 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 20.04 LTS curl No fix yet —
Ubuntu Pro 18.04 LTS curl No fix yet —
Ubuntu Pro 16.04 LTS curl No fix yet —
Ubuntu Pro 14.04 LTS curl No fix yet —

Red Hat

Security tracker ↗
ReleasePackageFixed inAdvisory
RHEL 10 curl +3 8.12.1-4.el10_2.7 RHSA-2026:80512
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Red Hat Hardened Images 1 curl +3 8.20.0-0.1.hum1 RHSA-2026:12916

AlmaLinux

Errata ↗
ReleasePackageFixed inAdvisory
AlmaLinux 10 curl +3 8.12.1-4.el10_2.7 ALSA-2026:80512

Rocky Linux

Errata ↗
ReleasePackageFixed inAdvisory
Rocky Linux 10 curl 8.12.1-4.el10_2.7 RLSA-2026:80512

SUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
SLES 15 SP7 curl 8.14.1-150700.7.23.1 SUSE-SU-2026:3798-1
SLES 12 SP5 curl 8.0.1-11.123.1 SUSE-SU-2026:2703-1
Show 3 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 curl +1 8.14.1-160000.6.1 SUSE-SU-2026:22156-1
SLES 16.0 curl +1 8.14.1-160000.6.1 SUSE-SU-2026:22156-1
SLE Micro 6.2 curl 8.14.1-160000.6.1 SUSE-SU-2026:22146-1

openSUSE

Security tracker ↗
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed curl 8.20.0-1.1 openSUSE-SU-2026:10674-1
openSUSE Leap 16.0 curl 8.14.1-160000.6.1 openSUSE-SU-2026:20973-1

Alpine

Security tracker ↗
ReleasePackageFixed inAdvisory
Alpine v3.24 curl 8.20.0-r0 —
Alpine v3.23 curl 8.20.0-r0 —
Alpine v3.22 curl 8.14.1-r4 —
Alpine v3.21 curl 8.14.1-r3 —

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 cmake 3.30.3-14 —
Azure Linux 3 curl 8.11.1-9 —

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 10 curl +3 8.12.1-4.el10_2.7 ELSA-2026-80512

Advisories 12

References