CVE-2026-49214

Technical Description

guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Versions prior to 2.10.2 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. A vulnerable flow is: First, an application accepts a user-controlled URL. Second, the URL is used to construct a PSR-7 `Uri` or `Request`. Third, the host component contains CRLF or another header-unsafe character. Fourth, the host is copied into the PSR-7 `Host` header when no explicit `Host` header is provided. Finally, the request is serialized or sent by an HTTP client that does not independently reject the malformed host. In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing `"\r\nX-Injected: yes"` can cause the generated `Host` header to span multiple HTTP header lines. Applications are affected when they use user-controlled URLs for outbound HTTP requests, URL forwarding, proxying, crawling, webhook

Remediation

Check the references section for vendor advisories and patches from guzzlephp. Update psr-7 to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References