Authentication Bypass by Capture-replay in cURL - CVE-2026-8927
Published: June 24, 2026
Vulnerability identifier: #VU135077
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-8927
CWE-ID: CWE-294
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: curl.haxx.se
Affected software:
cURL
cURL
Detailed vulnerability description
The vulnerability allows a remote user to impersonate the client to another proxy.
The vulnerability exists due to authentication bypass by capture-replay in libcurl proxy authentication state handling when reusing a libcurl handle for sequential transfers driven by environment-variable proxy configuration. A remote user can receive a leaked Proxy-Authorization header on a subsequent request to impersonate the client to another proxy.
The issue affects libcurl and does not affect the curl command line tool.
How to mitigate CVE-2026-8927
Install security update from vendor's website.