Vulnerability Description
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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Guzzlephp | Guzzle | < 7.12.1 |
Related Weaknesses (CWE)
References
- https://github.com/guzzle/guzzle/security/advisories/GHSA-wpwq-4j6v-78m3Third Party Advisory
FAQ
What is CVE-2026-55568?
CVE-2026-55568 is a vulnerability with a CVSS score of 5.9 (MEDIUM). 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 c...
How severe is CVE-2026-55568?
CVE-2026-55568 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-55568?
Check the references section above for vendor advisories and patch information. Affected products include: Guzzlephp Guzzle.