Exposure of Data Element to Wrong Session in cURL - CVE-2026-86411
Published: October 14, 2026
Vulnerability identifier: #VU155690
CSH Severity: Low
CVSS v4: 0 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-86411
CWE-ID: CWE-488
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to perform FTP transfers under another handle's client-certificate identity.
The vulnerability exists due to exposure of authentication state to the wrong session in libcurl's FTP connection reuse logic when reusing a pooled control connection previously upgraded with STARTTLS and authenticated using a client certificate. A local user can initiate an ftp:// transfer configured with CURLUSESSL_NONE using that connection pool to perform FTP transfers under another handle's client-certificate identity.
The second handle performs neither a new TLS handshake nor a new FTP login.
Affected software
cURL
How to mitigate CVE-2026-86411
Install security update from vendor's website.
cURL - update to 8.22.0