Is This vulnerability exploited in the wild?

No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

How severe is This vulnerability?

Medium severity, with a CVSS score of 5.9, published 1 August 2026.

Which products and versions are affected?

Guzzle < 7.15.1; guzzlehttp/guzzle (Packagist) < 7.15.1.

Is there a fix for This vulnerability?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is This vulnerability attacked?

It is attacked over the network, in a software library.

Check whether you run Guzzle or guzzlehttp/guzzle (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Guzzle information disclosure in RedirectMiddleware Referer headers

Q: Which products and versions are affected?

Guzzle < 7.15.1; guzzlehttp/guzzle (Packagist) < 7.15.1.

Q: Is there a fix for This vulnerability?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

Q: How is This vulnerability attacked?

It is attacked over the network, in a software library.

Q: Am I affected?

Check whether you run Guzzle or guzzlehttp/guzzle (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Severity: medium · CVSS 5.9 · Published 2026-08-01

Guzzle, a popular PHP HTTP client library, contains a flaw that can leak sensitive information during web redirects. When a specific optional setting is enabled, the library may include private data from a web address (like access tokens or login secrets) in headers sent to a new destination. An attacker who controls a redirect destination could capture this sensitive information, potentially leading to account takeover or data theft.

Technologies: Guzzle, guzzlehttp/guzzle (Packagist). Vendors: Guzzle, Packagist.

Quick answers

Is This vulnerability exploited in the wild?: No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?: Medium severity, with a CVSS score of 5.9, published 1 August 2026.
Which products and versions are affected?: Guzzle < 7.15.1; guzzlehttp/guzzle (Packagist) < 7.15.1.
Is there a fix for This vulnerability?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is This vulnerability attacked?: It is attacked over the network, in a software library.
Am I affected?: Check whether you run Guzzle or guzzlehttp/guzzle (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An information disclosure vulnerability exists in Guzzle's RedirectMiddleware (versions < 7.15.1) when the optional 'allow_redirects.referer' setting is enabled. The middleware incorrectly includes the URI fragment (the portion after the '#') in the generated Referer header when following same-scheme redirects (e.g., HTTPS to HTTPS). While fragments are normally handled locally by clients and omitted from HTTP requests, Guzzle's reintroduction of them allows a malicious redirect destination to capture sensitive data such as OAuth tokens or session states. The vulnerability is exploitable if an application uses sensitive fragments and follows a redirect to an untrusted server. This is fixed in version 7.15.1 by stripping fragments before header generation.

Affected products

guzzlehttp guzzle < 7.15.1

Timeline

2026-07-18: advisory: Original GHSA-h95v-h523-3mw8 published
2026-08-01: disclosed: CVE-2026-67354 published
2026-08-04: other: Duplicate advisory GHSA-mqq9-gxg5-m58g withdrawn

References

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