CVE-2019-5418 in Ruby on Rails
Summary
by MITRE
There is a File Content Disclosure vulnerability in Action View <5.2.2.1, <5.1.6.2, <5.0.7.2, <4.2.11.1 and v3 where specially crafted accept headers can cause contents of arbitrary files on the target system's filesystem to be exposed.
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Analysis
by VulDB Data Team • 10/30/2025
The vulnerability identified as CVE-2019-5418 represents a critical file content disclosure flaw within the Action View component of Ruby on Rails frameworks. This vulnerability specifically affects versions prior to the mentioned secure releases, creating a significant security risk for applications that rely on the framework's rendering capabilities. The flaw stems from improper handling of accept headers in the framework's content negotiation process, which allows attackers to manipulate the system into revealing sensitive file contents from the target server's filesystem.
The technical exploitation mechanism of this vulnerability involves crafting specially formatted accept headers that trick the Action View component into processing file content through its rendering pipeline. When an application receives a request with a malicious accept header, the framework's content negotiation logic fails to properly validate or sanitize the input, leading to unintended file access patterns. This occurs because the framework's default behavior for handling certain content types does not adequately restrict file system access, allowing attackers to specify arbitrary file paths that should remain protected. The vulnerability specifically targets the framework's ability to handle file content rendering, particularly when dealing with template and asset files that may contain sensitive information.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose critical system files including configuration files, database credentials, source code repositories, and other sensitive artifacts. Attackers can leverage this vulnerability to gain unauthorized access to system resources that should remain isolated from public access, potentially leading to complete system compromise. The vulnerability affects multiple versions of the Ruby on Rails framework, creating widespread exposure across numerous applications that have not yet been updated to secure releases. This type of vulnerability aligns with CWE-200, which categorizes improper output neutralization for logs, and represents a classic example of insecure direct object reference issues that can escalate to more severe security breaches.
Organizations affected by this vulnerability should prioritize immediate patching of their Ruby on Rails applications to versions 5.2.2.1, 5.1.6.2, 5.0.7.2, 4.2.11.1, and 3.2.22.5 respectively. The mitigation strategy should include comprehensive testing of the patched versions to ensure no regression in application functionality while implementing proper input validation for accept headers. Additional defensive measures such as web application firewalls and network-level restrictions can provide layered protection against exploitation attempts. Security teams should also conduct thorough audits of their application code to identify any custom implementations that might be vulnerable to similar file access patterns. This vulnerability demonstrates the importance of proper content type handling and input validation in web frameworks, aligning with ATT&CK technique T1213 for Data from Information Repositories and T1083 for File and Directory Discovery, which are commonly employed by threat actors to enumerate system resources and extract sensitive information.