Proxy-Authorization Header Disclosure in GuzzleHTTP by Guzzle

CVE-2026-67339

What is CVE-2026-67339?

The vulnerability in GuzzleHTTP affects versions prior to 7.14.2, where improper isolation of Proxy-Authorization headers from origin servers in cURL handlers can occur. This flaw enables attackers to potentially capture sensitive proxy credentials via origin server access logs, particularly when requests are either redirected, bypassed, or sent through SOCKS proxies that are incorrectly identified as direct connections by Guzzle. This can lead to unauthorized access and exploitation of sensitive data.

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