Is CVE-2026-66339 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-66339?

CVE-2026-66339 has a CVSS v3 severity of MEDIUM (6.5).

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CVE-2026-66339

Description

A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel to the destination server. This allows the destination server to capture proxy credentials, leading to information disclosure.