Ruby on Rails Action View Arbitrary File Content Disclosure Vulnerability (CVE-2019-5418) Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTRuby on Rails Action View versions prior to 5.2.2.1, 5.1.6.2, 5.0.7.2, 4.2.11.1, and all v3 versions
Unauthenticated remote attackers can exploit specially crafted Accept headers to read arbitrary files from the target system's filesystem, leading to sensitive data exposure
Immediately upgrade Ruby on Rails and Action View to the patched versions, or apply temporary web server filtering rules
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update your project's Gemfile to specify a secure version of Rails and Action View, then run bundler to apply the update.
# Update Gemfile to secure versions
# gem 'rails', '>= 5.2.2.1'
# Execute dependency update
bundle update actionview rails2. Temporary Workaround & Hardening Configuration
If an immediate upgrade is not feasible, configure your reverse proxy (e.g., Nginx) to block requests containing directory traversal patterns in the Accept header.
# Block malicious Accept headers at the Nginx level
server {
listen 80;
server_name your-rails-app.com;
if ($http_accept ~* '\.\./') {
return 400 'Invalid Accept Header';
}
}3. Log Audit & IoC Verification Commands
Scan your web server access logs for potential exploitation attempts targeting the Accept header.
# Search access logs for directory traversal patterns in headers
grep -i '\.\./' /var/log/nginx/access.log
# Verify the currently installed actionview version
bundle info actionviewScan Your Repositories for Transitive Vulnerable Dependencies in 30 Seconds
Automatically detect vulnerable packages across npm, PyPI, Maven, and Go, and open automated fix Pull Requests without breaking your build.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2019-5418) is a directory traversal and file disclosure flaw in Action View, the template rendering component of the Ruby on Rails framework. Action View determines which template to render based on the format specified in the HTTP 'Accept' header. Due to insufficient validation and sanitization of this header input, the rendering engine directly processes user-supplied relative path sequences, allowing directory traversal attacks.
2. Exploitation Mechanics & Attack Scenario
An attacker can craft a malicious HTTP request containing directory traversal sequences (e.g., '../../') within the 'Accept' header. When Action View attempts to locate the template corresponding to the requested format, it resolves the path relative to the template directory. Because of the lack of input sanitization, the application traverses out of the intended directory and reads arbitrary files (such as 'Accept: ../../../../../etc/passwd{{'). The contents of the targeted file are then returned in the HTTP response body.
3. Infrastructure & Business Impact
With its inclusion in the CISA KEV catalog and an EPSS score of 0.9851 (98.51%), this vulnerability is actively and widely exploited in the wild. Successful exploitation allows attackers to retrieve highly sensitive files, including database credentials ('config/database.yml'), application secrets ('config/credentials.yml.enc'), and system configuration files. This exposure often serves as a stepping stone for full database compromise or remote code execution (RCE), posing a severe threat to business continuity.
Official Vendor Advisories & References
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.
Frequently Asked SecOps Questions (CVE-2019-5418)
FAQQ1. How critical is CVE-2019-5418 and is it actively exploited in the wild?
CVE-2019-5418 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 98.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2019-5418?
Primary impacted vendors include rubyonrails across actionview, rails. Scope summary: Ruby on Rails Action View < 5.2.2.1, < 5.1.6.2, < 5.0.7.2, < 4.2.11.1, and v3
Q3. What temporary mitigations or workarounds exist for CVE-2019-5418 before patching?
[Mitigation] Immediately upgrade Ruby on Rails and Action View to the patched versions, or apply temporary web server filtering rules Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2019-5418
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
🔗 Related Advisories in Similar Stack (rubyonrails)
View Category →GitLab CE/EE Unauthenticated Arbitrary File Read Vulnerability (CVE-2026-85706)
[Affected Scope] GitLab CE/EE versions from 18.7 through 19.3.1.
JFrog Artifactory Path Traversal Vulnerability (CVE-2026-66384) Security Advisory: Arbitrary File Write via Docker Cache Path
[Affected Scope] JFrog Artifactory Self-Managed instances under specific remote-repository conditions
sevenz-rust2 Path Traversal and Arbitrary File Overwrite Vulnerability (CVE-2026-61725)
[Affected Scope] Rust applications utilizing sevenz-rust2 library versions prior to 0.21.1.
GitLab CE/EE Unauthenticated Remote Code Execution (RCE) Advisory (CVE-2026-97229)
[Affected Scope] GitLab CE/EE versions 19.2 (< 19.2.8), 19.3 (< 19.3.5), and 19.4 (< 19.4.2)
Subscribe to Daily Vulnerability Briefings & KEV Alerts
Concise morning briefings for SecOps, DevSecOps, and SRE teams covering newly exploited CVEs and mitigation priorities.