Insertion of Sensitive Information Into Sent Data in cURL - CVE-2026-86414
Published: October 14, 2026
Vulnerability identifier: #VU155687
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-86414
CWE-ID: CWE-201
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose origin credentials.
The vulnerability exists due to incorrect handling of origin authentication challenges in libcurl's HTTP proxy tunnel handling when processing responses to CONNECT requests. A remote attacker can return an HTTP 401 response with a WWW-Authenticate header instead of the expected HTTP 407 response with a Proxy-Authenticate header to disclose origin credentials.
Exploitation requires the client to use an attacker-controlled HTTP proxy. Exposed credentials can include a Basic authentication password or a Negotiate/Kerberos ticket.
Affected software
cURL
How to mitigate CVE-2026-86414
Install security update from vendor's website.
cURL - update to 8.23.0