CVE-2026-48998 guzzlehttp/psr7 has Host Confusion via Authority Reinterpretation
Attackers can bypass host validation in Guzzle PSR7 by crafting malformed Host headers, potentially causing requests to be sent to unintended hosts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48998?
CVE-2026-48998 is a medium-severity server-side request forgery vulnerability in guzzle psr7, published on 11 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Versions prior to 2.10.2 contain improper Host header validation when parsing raw HTTP request messages and when deriving a server request URI from server variables. An attacker can provide a malformed Host header containing URI authority delimiters, such as `[email protected]`. When the Host value is used to construct a URI, the malformed value can be reinterpreted as URI userinfo and host. This can cause the PSR-7 request URI host to differ from the original Host header value. Applications are affected if they parse attacker-controlled raw HTTP requests with `GuzzleHttp\Psr7\Message::parseRequest()` or the legacy 1.x `GuzzleHttp\Psr7\parse_request()` function, or if they build server requests from attacker-controlled server variables, then rely on the resulting URI host for routing, allow-list checks, or forwarding decisions. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host. The issue is patched in `2.10.2`. `1.x` is end-of-life and will not receive a patch. Some workarounds are available. Validate the `Host` header as `uri-host [ ":" port ]` before calling `Message::parseRequest()` or legacy `parse_request()` on untrusted HTTP request data, or before deriving routing and forwarding decisions from a parsed request URI. Reject Host values containing userinfo, path, query, or fragment delimiters.
Which versions are affected by CVE-2026-48998?
2 open source packages ship an affected version, including guzzlehttp/psr7. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
guzzlehttp/psr7 Packagist | All versions | 2.10.2 |
guzzlehttp/psr7 Packagist | All versions | 2.10.2 |
Products include Guzzlephp Psr-7.
How do I fix CVE-2026-48998?
Upgrade guzzlehttp/psr7 to 2.10.2 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-48998 being exploited?
There is no known exploitation of CVE-2026-48998 in the wild and no public exploit code.
Other vulnerabilities in guzzle psr7
Sources
Also known as DEBIAN-CVE-2026-48998, GHSA-34xg-wgjx-8xph, MINI-34h9-3f4r-3hr5, MINI-3q3r-484q-wwj8, MINI-3v9r-v6hg-52w6, MINI-84cp-2928-pfp9 and 4 more.