CVE-2026-54171 in Excon
Summary
by MITRE • 07/17/2026
Excon is usable, fast, simple HTTP 1.1 for Ruby. Prior to 1.5.0, Excon's RedirectFollower middleware failed to strip additional sensitive headers when following redirects and did not provide a custom list of headers to strip. This could cause inadvertent leakage of sensitive data when the initial request includes header information that is not intended for the new target. This issue is fixed in version 1.5.0.
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Analysis
by VulDB Data Team • 07/17/2026
The vulnerability identified in Excon versions prior to 1.5.0 represents a critical security flaw in HTTP redirect handling mechanisms that directly impacts data confidentiality and privacy protection. This issue manifests within the RedirectFollower middleware component, which is responsible for managing HTTP redirects from one URL to another during web requests. The flaw specifically occurs when the middleware processes redirects and fails to properly sanitize sensitive header information that may be present in the original request. When Excon follows a redirect, it should strip headers containing authentication tokens, session identifiers, or other confidential data that could inadvertently be transmitted to a different host or domain.
The technical nature of this vulnerability aligns with CWE-200, which describes improper exposure of sensitive information through header leakage, and CWE-532, which addresses insertion of sensitive information into log files. The flaw represents a classic case of insufficient input sanitization during HTTP redirection processes where the middleware does not implement proper header filtering mechanisms. Without a configurable list of headers to strip, the system defaults to preserving all headers from the original request, including those that contain sensitive data such as authorization tokens, cookies, or custom authentication headers that should never be transmitted to external domains.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable privilege escalation attacks and session hijacking scenarios. When an application using Excon makes a request that triggers a redirect to a third-party domain, any sensitive headers present in the original request will be automatically forwarded to the new destination without proper sanitization. This creates significant risk for applications handling authentication tokens, API keys, or other confidential information within HTTP headers, as these credentials could be exposed to unintended recipients during legitimate redirect operations.
Security practitioners should note that this vulnerability directly relates to ATT&CK technique T1566.002, which covers the use of phishing with redirects and the exploitation of HTTP redirect mechanisms for malicious purposes. The lack of configurable header stripping capabilities in Excon's middleware means that organizations using this library may unknowingly expose sensitive information during normal operational procedures, creating potential attack vectors for adversaries who can manipulate redirect destinations to capture this leaked data.
Mitigation strategies should begin with immediate upgrading to Excon version 1.5.0 or later, which implements proper header sanitization during redirect operations. Organizations should also implement additional monitoring and logging controls to detect anomalous redirect behavior that could indicate potential exploitation attempts. Security teams should review their applications' HTTP request patterns to identify instances where sensitive headers might be present in requests that could trigger redirects, and consider implementing custom middleware solutions that provide more granular control over header handling during redirect operations.
The fix implemented in version 1.5.0 addresses the core issue by introducing proper header stripping functionality and providing developers with the ability to configure which headers should be removed during redirect processing. This enhancement aligns with security best practices outlined in OWASP's secure coding guidelines for HTTP communication, particularly those addressing information leakage through improper header handling during web application operations. Organizations should also consider implementing network-level controls such as proxy configurations or API gateways that can provide additional layers of protection against sensitive data exposure during redirect operations, ensuring comprehensive defense-in-depth strategies are employed to protect against similar vulnerabilities across their infrastructure.