Improper validation of certificate with host mismatch in cURL - CVE-2026-12064

Vulnerability identifier: #VU135080

CSH Severity: Medium

CVSS v4: 4.6 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-12064

CWE-ID: CWE-297

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to connect to an unverified SSH remote host.

The vulnerability exists due to improper validation of certificate with host mismatch in the curl command line tool when processing a schemeless URL combined with --proto-default for sftp or scp. A remote attacker can present an SSH server in that connection flow to connect to an unverified SSH remote host.

This issue affects only the curl command line tool and does not affect other users of libcurl or the libcurl library itself.

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

Install security update from vendor's website.

cURL - update to 8.21.0
LANTIME Operating System Firmware (LTOS) - update to 7.10.013
curl (Ubuntu package) - addressed in versions 7.35.0-1ubuntu2.20+esm21, 7.47.0-1ubuntu2.19+esm17, 7.58.0-2ubuntu3.24+esm10, 7.68.0-1ubuntu2.25+esm5, 8.5.0-2ubuntu10.11, 8.14.1-2ubuntu1.5, 8.18.0-1ubuntu2.3
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-debuginfo - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
curl - addressed in versions 7.71.1-52, 7.79.1-53, 8.4.0-35
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-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-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
libcurl4-64bit-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-debuginfo - 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-mini-debugsource - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
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-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 8.15.0-9.fc43, 8.18.0-9.fc44

• https://curl.se/docs/CVE-2026-12064.html
• https://github.com/curl/curl/commit/ab3bb8cd8be8f9d4acb97da041

• Multiple vulnerabilities in cURL
• Ubuntu update for curl
• SUSE update for curl
• SUSE update for curl
• SUSE 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