Improper Certificate Validation in cURL - CVE-2026-8286

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Main Vulnerability Database Vulnerabilities #VU135081

Improper Certificate Validation in cURL - CVE-2026-8286

Published: June 24, 2026


Vulnerability identifier: #VU135081
CSH Severity: Medium
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-8286
CWE-ID: CWE-295
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to bypass TLS certificate validation.

The vulnerability exists due to improper certificate validation in connection reuse logic for STARTTLS-enabled protocol handling when reusing an existing live connection for a new transfer. A remote attacker can cause a transfer to reuse a connection with mismatched TLS settings to bypass TLS certificate validation.

This affects transfers using IMAP, POP3, SMTP, FTP, or LDAP schemes that begin in cleartext and are upgraded to TLS with STARTTLS.


Affected software

cURL
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
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
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Anolis OS
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
Fedora
LANTIME Operating System Firmware (LTOS)
curl (Ubuntu package)
curl (Red Hat package)
libcurl-minimal
curl-doc
libcurl-devel
libcurl
curl-minimal
curl
curl-debuginfo
curl-help
curl-debugsource
libcurl4
libcurl4-32bit
libcurl4-debuginfo
libcurl4-debuginfo-32bit
libcurl4-64bit-debuginfo
libcurl4-32bit-debuginfo
curl-mini-debugsource
libcurl-mini4-debuginfo
libcurl-devel-32bit
curl-zsh-completion
libcurl-devel-doc
curl-fish-completion
libcurl4-64bit
libcurl-devel-64bit
libcurl-mini4

How to mitigate CVE-2026-8286

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+esm20, 7.35.0-1ubuntu2.20+esm23, 7.47.0-1ubuntu2.19+esm16, 7.58.0-2ubuntu3.24+esm9, 7.68.0-1ubuntu2.25+esm4, 7.81.0-1ubuntu1.25, 8.5.0-2ubuntu10.10, 8.14.1-2ubuntu1.4, 8.18.0-1ubuntu2.2
curl (Red Hat package) - addressed in versions 7.61.1-34.el8_10.13, 8.12.1-1.el10_0.10
libcurl-minimal - addressed in versions 7.61.1-35.0.2, 8.4.0-28
curl-doc - addressed in versions 7.61.1-35.0.2, 8.4.0-28
libcurl-devel - addressed in versions 7.61.1-35.0.2, 8.4.0-28
libcurl - addressed in versions 7.61.1-35.0.2, 8.4.0-28
curl-minimal - addressed in versions 7.61.1-35.0.2, 8.4.0-28
curl - addressed in versions 7.61.1-35.0.2, 8.4.0-28
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-help - 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
libcurl - 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
libcurl4 - addressed in versions 8.0.1-11.126.1, 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 8.0.1-11.126.1, 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 8.0.1-11.126.1, 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 8.0.1-11.126.1, 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 8.0.1-11.126.1, 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 8.0.1-11.126.1, 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 8.0.1-11.126.1, 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1, 8.14.1-150700.7.20.1
libcurl4-debuginfo-32bit - update to 8.0.1-11.126.1
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
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
libcurl-devel-32bit - 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-doc - 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
libcurl4-64bit - addressed in versions 8.14.1-150400.5.86.1, 8.14.1-150600.4.46.1
libcurl-devel-64bit - 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

External References

Related Security Bulletins