# CVE-2026-67339: guzzlehttp Guzzle Proxy-Authorization header disclosure

Source: https://junglewise.ai/threats/cve-2026-67339-guzzlehttp-guzzle-proxy-authorization-header-disclosure  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-01. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-67339 · Severity: medium · CVSS 5.3 · Published 2026-08-01

Guzzle is a popular PHP HTTP client library used by applications to make web requests. A flaw in versions before 7.14.2 causes proxy authentication credentials (Proxy-Authorization headers) to be inadvertently sent to origin servers instead of being kept private for the proxy. An attacker controlling a web server that receives a redirected request could capture these credentials through access logs and potentially abuse the proxy to reach restricted resources or impersonate legitimate users.

Technologies: [guzzlehttp/guzzle (Packagist)](https://junglewise.ai/threats/technologies/guzzlehttp-guzzle). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is CVE-2026-67339 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-67339 being exploited in the wild.

**How severe is CVE-2026-67339?** Medium severity, with a CVSS score of 5.3, published 1 August 2026.

**Which products and versions are affected?** guzzlehttp/guzzle (Packagist) ECOSYSTEM:introduced=0,fixed=7.14.2.

**Is there a fix for CVE-2026-67339?** Yes. guzzlehttp/guzzle (Packagist): upgrade to 7.14.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-67339 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-67339?** Check whether you run 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.

## How to fix

- guzzlehttp/guzzle (Packagist): upgrade to 7.14.2 or later

  ```sh
  composer require guzzlehttp/guzzle:^7.14.2
  ```


## Technical details

The vulnerability is a sensitive information disclosure (CWE-200) in the cURL handlers (CurlHandler and CurlMultiHandler) of Guzzle. The root cause is that Guzzle incorrectly places Proxy-Authorization headers in cURL's origin header list (CURLOPT_HTTPHEADER) instead of the proxy-only list (CURLOPT_PROXYHEADER) when certain routing conditions occur: direct connections, proxy-bypassed requests (via no_proxy rules), or SOCKS proxies misclassified as direct. The vulnerability also occurs when redirect middleware re-evaluates proxy routing but fails to strip Proxy-Authorization. An attacker can exploit this by controlling an origin server (via redirect or direct access) to capture proxy credentials in access logs. Attack vector is network-based with no authentication required. Patch available in version 7.14.2.

## Affected products

- guzzlehttp Guzzle before 7.14.2

## Identifiers

- CVE-2026-67339
- GHSA-94pj-82f3-465w

## Timeline

- 2026-07-14: disclosed
- 2026-08-01: advisory: Published on NVD and VulnCheck
- 2026-07-14: patched: Fix released in version 7.14.2

## References

- [https://github.com/guzzle/guzzle/security/advisories/GHSA-94pj-82f3-465w](https://github.com/guzzle/guzzle/security/advisories/GHSA-94pj-82f3-465w)
- [https://www.vulncheck.com/advisories/guzzlehttp-guzzle-before-proxy-authorization-header-disclosure](https://www.vulncheck.com/advisories/guzzlehttp-guzzle-before-proxy-authorization-header-disclosure)

## Related threats

- [Guzzle noncanonical host bypass in URI handlers](https://junglewise.ai/threats/cve-2026-69246-guzzle-noncanonical-host-bypass-in-uri-handlers)
- [Guzzle incorrect cookie domain matching for noncanonical IP addresses](https://junglewise.ai/threats/cve-2026-69245-guzzle-incorrect-cookie-domain-matching-for-noncanonical-ip)
- [Guzzle GuzzleHTTP host-only cookie scope disclosure](https://junglewise.ai/threats/guzzle-guzzlehttp-host-only-cookie-scope-disclosure-958db8d5)
- [Guzzle information disclosure in RedirectMiddleware Referer headers](https://junglewise.ai/threats/guzzle-information-disclosure-in-redirectmiddleware-referer-headers-d2e711b6)
- [Guzzle unbounded response cookies denial of service in CookieJar](https://junglewise.ai/threats/guzzle-unbounded-response-cookies-denial-of-service-in-cookiejar-f650c2bc)