CVE-2026-25765: Faraday affected by SSRF via protocol-relative URL host override in build_exclusive_url

Severity: medium (CVSS 5.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-09 · updated 2026-06-17
Weakness: CWE-918

Description

Faraday is an HTTP client library abstraction layer that provides a common interface over many adapters. Prior to 2.14.1, Faraday's build_exclusive_url method (in lib/faraday/connection.rb) uses Ruby's URI#merge to combine the connection's base URL with a user-supplied path. Per RFC 3986, protocol-relative URLs (e.g. //evil.com/path) are treated as network-path references that override the base URL's host/authority component. This means that if any application passes user-controlled input to Faraday's get(), post(), build_url(), or other request methods, an attacker can supply a protocol-relative URL like //attacker.com/endpoint to redirect the request to an arbitrary host, enabling Server-Side Request Forgery (SSRF). This vulnerability is fixed in 2.14.1.

Affected products

lostisland faraday: from 1.0.0 before 1.10.5; from 2.0.0 before 2.14.1 — fixed in 1.10.5, 2.14.1

How to fix

Upgrade to a fixed version: lostisland faraday 1.10.5, 2.14.1. Check the vendor advisory for mitigations.

References

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