CVE-2026-55568 Details
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.
A vulnerability in Guzzle, a PHP HTTP client, prior to version 7.12.1, allows for traffic expected to be protected by TLS to be transmitted in cleartext when using an 'https://' proxy with certain configurations. This issue arises because the built-in cURL handlers, 'GuzzleHttp\Handler\CurlHandler' and 'GuzzleHttp\Handler\CurlMultiHandler', treat 'https://' proxies as plaintext 'http://' proxies when libcurl is older than 7.50.2', leading to an unencrypted proxy leg. As a result, proxy authentication credentials are sent without encryption, and the CONNECT target host and port for tunneled HTTPS requests are exposed. This vulnerability affects applications that send requests through the cURL handlers, configure an 'https://' proxy expecting encryption, and run with libcurl older than 7.50.2.
Users can upgrade to Guzzle version 7.12.1 or later, where this vulnerability is patched. If an immediate upgrade is not possible, do not configure an 'https://' proxy on systems with an unsupported libcurl version. Instead, verify the libcurl version and its support for HTTPS proxies before using such a proxy. Instructions for checking the libcurl version and proxy support are available in the Guzzle vulnerability advisory.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/guzzle/guzzle/security/advisories/GHSA-wpwq-4j6v-78m3 | [email protected] | Third Party Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-311 | Missing Encryption of Sensitive Data | [email protected] |
| CWE-319 | Cleartext Transmission of Sensitive Information | [email protected] |
| CWE-636 | Not Failing Securely ('Failing Open') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| guzzlephp guzzle | < 7.12.1 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 26, 2026 | Initial Analysis | [email protected] |
| Jun 23, 2026 | CVE Modified | CISA-ADP |
| Jun 23, 2026 | New CVE Received | [email protected] |