Insertion of Sensitive Information Into Sent Data in cURL - CVE-2026-86409
Published: October 14, 2026
Vulnerability identifier: #VU155692
CSH Severity: Low
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-86409
CWE-ID: CWE-201
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose an access-key identifier and a request-bound signature.
The vulnerability exists due to failure to disable SigV4 authentication in libcurl's SigV4 authentication handling when an application sets CURLOPT_AWS_SIGV4 to NULL and reuses the same easy handle while retaining CURLOPT_USERPWD credentials. A remote attacker can influence the destination URL of a subsequent request to disclose an access-key identifier and a request-bound signature.
The secret key is not transmitted. This flaw is not accessible through the curl command line tool.
Affected software
cURL
How to mitigate CVE-2026-86409
Install security update from vendor's website.
cURL - update to 8.22.0