Ruby on Rails Action View Directory Traversal and Remote Code Execution (CVE-2016-0752)
Executive & SecOps Summary
SECOPS ASSESSMENTRuby on Rails versions before 3.2.22.1, 4.0.x, 4.1.x before 4.1.14.1, 4.2.x before 4.2.5.1, and 5.x before 5.0.0.beta1.1
Remote attackers can read arbitrary files or potentially execute arbitrary code by exploiting unrestricted input parameters passed to the render method
Immediately upgrade the Ruby on Rails framework and Action View gem to the patched official release versions
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update your project's Gemfile to specify the secure patched version of Rails, then run Bundler to apply the updates.
# Update Gemfile with the appropriate secure version
# gem 'rails', '4.2.5.1'
# Run bundler to update the specific gems
bundle update rails actionview2. Temporary Workaround & Hardening Configuration
If patching cannot be applied immediately, implement strict input validation using an explicit whitelist in your controllers to prevent arbitrary file rendering.
# Example of controller-level whitelist validation
class PagesController < ApplicationController
def show
allowed_pages = ['about', 'contact', 'home']
page = params[:page]
if allowed_pages.include?(page)
render template: "pages/#{page}"
else
render file: 'public/404.html', status: :not_found
end
end
end3. Log Audit & IoC Verification Commands
Verify the currently installed version of Action View and inspect web server access logs for directory traversal patterns.
# 1. Check the installed version of Action View
bundle info actionview | grep -E 'actionview|Version'
# 2. Scan web server access logs for directory traversal attempts
grep -Ei '\.\./|\.%2e%2e%2f|%2e%2e%2f' /var/log/nginx/access.log /var/log/apache2/access.log 2>/dev/nullScan Your Repositories for Transitive Vulnerable Dependencies in 30 Seconds
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2016-0752) is a critical directory traversal flaw in the Action View component of Ruby on Rails. It occurs when an application accepts untrusted user input and passes it directly to the render method without proper sanitization. Because Action View's template resolution mechanism fails to adequately filter directory traversal sequences (such as ..), an attacker can force the application to render arbitrary files outside the intended template directory.
2. Exploitation Mechanics & Attack Scenario
An attacker sends a crafted HTTP request containing directory traversal sequences (e.g., ../) in parameters that are subsequently processed by a vulnerable controller action like render params[:page]. Action View attempts to locate and render the file specified by the path. This allows the attacker to read sensitive system files such as /etc/passwd. Furthermore, if the attacker can inject malicious Ruby code into a local file (such as application logs or session files), they can leverage this traversal vulnerability to render that file, leading to Remote Code Execution (RCE).
3. Infrastructure & Business Impact
As a vulnerability listed in the CISA KEV catalog with an extremely high EPSS score, this flaw is actively targeted in the wild. Successful exploitation can lead to the exposure of sensitive configuration files, database credentials, and source code. If escalated to Remote Code Execution, attackers can compromise the entire web server, establish persistence, pivot into internal networks, or deploy ransomware.
Official Vendor Advisories & References
Directory traversal vulnerability in Action View in Ruby on Rails before 3.2.22.1, 4.0.x and 4.1.x before 4.1.14.1, 4.2.x before 4.2.5.1, and 5.x before 5.0.0.beta1.1 allows remote attackers to read arbitrary files by leveraging an application's unrestricted use of the render method and providing a .. (dot dot) in a pathname.
Frequently Asked SecOps Questions (CVE-2016-0752)
FAQQ1. How critical is CVE-2016-0752 and is it actively exploited in the wild?
CVE-2016-0752 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 95.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2016-0752?
Primary impacted vendors include rubyonrails across rails, actionview. Scope summary: Ruby on Rails versions before 3.2.22.1, 4.0.x, 4.1.x before 4.1.14.1, 4.2.x before 4.2.5.1, and 5.x before 5.0.0.beta1.1
Q3. What temporary mitigations or workarounds exist for CVE-2016-0752 before patching?
[Mitigation] Immediately upgrade the Ruby on Rails framework and Action View gem to the patched official release versions 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-2016-0752
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