Guzzle up to 7.12.0 PHP cURL Extension missing encryption

Summaryinfo

A vulnerability classified as problematic was found in Guzzle up to 7.12.0. The impacted element is an unknown function of the component PHP cURL Extension. The manipulation results in missing encryption. This vulnerability was named CVE-2026-55568. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Guzzle up to 7.12.0. Affected is an unknown function of the component PHP cURL Extension. The manipulation with an unknown input leads to a missing encryption vulnerability. CWE is classifying the issue as CWE-311. The product does not encrypt sensitive or critical information before storage or transmission. This is going to have an impact on confidentiality. CVE summarizes:

Guzzle is an extensible PHP HTTP client. Prior to 7.12.1, in certain configurations, traffic expected to be protected by TLS on the hop to the proxy is transmitted in cleartext. Proxy authentication credentials (the Proxy-Authorization header, proxy userinfo in the proxy URL, or CURLOPT_PROXYUSERPWD) are sent without encryption, and the CONNECT target host and port for tunneled HTTPS requests are exposed. The built-in cURL handlers (GuzzleHttp\Handler\CurlHandler and GuzzleHttp\Handler\CurlMultiHandler, used by default whenever the PHP cURL extension is available) accept an https:// proxy. libcurl older than 7.50.2 silently treats an https:// proxy as a plaintext http:// proxy. The TLS connection to the proxy is never established, and the proxy leg is cleartext with no error or warning. An application is affected when it sends requests through one of the built-in cURL handlers, configures an https:// proxy expecting the proxy connection itself to be encrypted, and runs with libcurl older than 7.50.2. This vulnerability is fixed in 7.12.1.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-55568 since 06/17/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1600 by the MITRE ATT&CK project.

Upgrading to version 7.12.1 eliminates this vulnerability.

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Productinfo

Name

• Guzzle

Version

• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5
• 7.6
• 7.7
• 7.8
• 7.9
• 7.10
• 7.11
• 7.12.0

Website

• Product: https://github.com/guzzle/guzzle/

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