CVE-2026-55568

A flaw was found in Guzzle, an extensible PHP HTTP client. In certain configurations, when an application uses Guzzle's built-in cURL handlers with an HTTPS proxy and an older version of libcurl prior to 7.50.2, traffic intended to be protected by TLS is transmitted in cleartext. This can lead to...

curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3 session tickets. When using a HTTPS proxy and TLS 1.3 libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote server and then wrongly "short-cut" the host handshake. When confusing the tickets a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed. Note that such a malicious HTTPS proxy needs to provide a certificate that curl will accept for the MITMed server for an attack to work - unless curl has been told to ignore the server certificate check.

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