What is CVE-2026-67339?

CVE-2026-67339 is a medium-severity vulnerability in Guzzle, classified under Information Disclosure. CVSS score: 5.3/10. Published 2026-08-01.

How severe is CVE-2026-67339?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Information disclosure in Guzzle

CVE-2026-67339

guzzlehttp/guzzle versions before 7.14.2 fail to properly isolate Proxy-Authorization headers from origin servers in cURL handlers. Attackers can capture proxy credentials through origin server access logs when requests are redirected, bypassed, or sent through SOCKS proxies that Guzzle misclassifies as direct connections.

Vulnerability class: Information Disclosure

EPSS: 0.002 (14.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

Affected products

Guzzle — versions 0, 7.14.2

Weakness classification (CWE)

CWE-200 — Information Disclosure

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-67339?: CVE-2026-67339 is a medium-severity vulnerability in Guzzle, classified under Information Disclosure. CVSS score: 5.3/10. Published 2026-08-01.
How severe is CVE-2026-67339?: Medium severity. CVSS v3 base score is 5.3 out of 10.