Authentication Bypass by Capture-replay in cURL - CVE-2026-8927

Vulnerability identifier: #VU135077

CSH Severity: Low

CVSS v4: 2.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-8927

CWE-ID: CWE-294

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote user to impersonate the client to another proxy.

The vulnerability exists due to authentication bypass by capture-replay in libcurl proxy authentication state handling when reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration. A remote user can receive a leaked Proxy-Authorization header on a subsequent request to impersonate the client to another proxy.

The issue affects libcurl and does not affect the curl command line tool.

cURL
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Manager Proxy
SUSE Manager Retail Branch Server
SUSE Manager Server
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Ubuntu
Basesystem Module
openSUSE Leap
openEuler
Anolis OS
Fedora
LANTIME Operating System Firmware (LTOS)
Red Hat OpenShift Dev Spaces
curl (Ubuntu package)
curl
curl-debuginfo
curl-debugsource
libcurl
libcurl-devel
curl-help
curl-doc
libcurl-minimal
curl-minimal
curl (Red Hat package)
libcurl-devel-64bit
libcurl4-64bit-debuginfo
libcurl4-32bit-debuginfo
libcurl4-32bit
libcurl4
libcurl4-debuginfo
curl-mini-debugsource
libcurl-mini4-debuginfo
libcurl4-64bit
curl-fish-completion
libcurl-devel-doc
curl-zsh-completion
libcurl-devel-32bit
libcurl-mini4

Install security update from vendor's website.

cURL - update to 8.21.0
LANTIME Operating System Firmware (LTOS) - update to 7.10.013
Red Hat OpenShift Dev Spaces - update to 3.30.1
curl (Ubuntu package) - addressed in versions 7.35.0-1ubuntu2.20+esm20, 7.35.0-1ubuntu2.20+esm23, 7.47.0-1ubuntu2.19+esm16, 7.47.0-1ubuntu2.19+esm20, 7.58.0-2ubuntu3.24+esm9, 7.58.0-2ubuntu3.24+esm14, 7.68.0-1ubuntu2.25+esm4, 7.68.0-1ubuntu2.25+esm9, 7.81.0-1ubuntu1.25, 7.81.0-1ubuntu1.29, 8.5.0-2ubuntu10.10, 8.5.0-2ubuntu10.15, 8.14.1-2ubuntu1.4, 8.18.0-1ubuntu2.2, 8.18.0-1ubuntu2.7
curl - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl-debuginfo - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl-debugsource - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
libcurl - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
libcurl-devel - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl-help - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl - update to 8.4.0-24
curl-doc - update to 8.4.0-24
libcurl-minimal - update to 8.4.0-24
libcurl-devel - update to 8.4.0-24
libcurl - update to 8.4.0-24
curl-minimal - update to 8.4.0-24
curl (Red Hat package) - update to 8.12.1-1.el10_0.10
libcurl-devel-64bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl4-64bit-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl4-32bit-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4-32bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4 - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl-devel - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl-debugsource - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
curl-mini-debugsource - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-mini4-debuginfo - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl4-64bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
curl-fish-completion - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-devel-doc - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
curl-zsh-completion - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-devel-32bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-mini4 - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
curl - addressed in versions 8.15.0-9.fc43, 8.18.0-9.fc44

• https://curl.se/docs/CVE-2026-8927.html
• https://github.com/curl/curl/commit/5c225384b8d52c6

• Multiple vulnerabilities in cURL
• Ubuntu update for curl
• SUSE update for curl
• SUSE update for curl
• SUSE update for curl
• Anolis OS update for curl
• Multiple vulnerabilities in Meinberg LANTIME firmware
• Fedora 44 update for curl
• Fedora 43 update for curl
• openEuler 24.03 LTS SP3 update for curl
• openEuler 24.03 LTS SP1 update for curl
• openEuler 22.03 LTS SP4 update for curl
• openEuler 20.03 LTS SP4 update for curl
• openEuler 24.03 LTS SP4 update for curl
• Red Hat Enterprise Linux 10 update for curl
• Multiple vulnerabilities in Red Hat OpenShift Dev Spaces 3.30
• Ubuntu update for curl
• Ubuntu update for curl