CISA Flags Exploited Ruby on Rails Path Traversal Flaw in Active Attacks

Ruby on Rails, a widely used web application framework, is facing renewed scrutiny after the disclosure of a severe path traversal vulnerability in its Action View component.

Security researchers have warned that this flaw, cataloged under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), can allow attackers to access sensitive files on affected servers by exploiting how Rails handles file rendering in conjunction with specially crafted HTTP headers.

Technical Details: Exploiting the render file: Call

The vulnerability arises when an application uses the render file: Method in Action View without adequate input validation.

Attackers can manipulate the HTTP Accept headers to inject directory traversal sequences such as ../, enabling them to traverse out of the intended directory and render arbitrary files on the server.

For example, a malicious request might look like:

textGET /vulnerable_endpoint HTTP/1.1
Host: victim.com
Accept: ../../../../etc/passwd

In Rails code, the unsafe pattern is:

ruby# Vulnerable usage
render file: params[:file]

If params[:file] is not properly sanitized, an attacker can supply a value like ../../../../etc/passwd, causing Rails to render and disclose the contents of /etc/passwd or other sensitive files.

Impact and Security Implications

Path traversal vulnerabilities like this one are particularly dangerous because they bypass directory restrictions and can expose configuration files, credentials, and other sensitive data.

CWE-22 is consistently ranked among the most dangerous software weaknesses due to its prevalence and the ease with which it can be exploited.

Attackers do not require sophisticated tools—simple crafted requests are often enough to access critical files.

While there is currently no public evidence linking this specific Rails vulnerability to ransomware campaigns, the potential for abuse is significant.

Unauthorized file disclosure could serve as a foothold for further attacks, including privilege escalation or lateral movement within compromised environments.

Mitigation Steps and Compliance Requirements

Administrators and developers are urged to take immediate action:

• Apply vendor patches and mitigations: Rails maintainers have released updates and advisories to address this flaw. Ensure all applications are running the latest secure version.
• Follow BOD 22-01 guidance: Per the Cybersecurity and Infrastructure Security Agency (CISA), organizations—especially those in the federal sector—must remediate vulnerabilities listed in the Known Exploited Vulnerabilities (KEV) catalog. This includes promptly applying patches or, if unavailable, discontinuing use of the affected product.
• Harden file rendering logic: Always validate and sanitize user input before using it in file paths. Prefer allowlists and avoid direct rendering of user-supplied paths.
• Monitor for suspicious activity: Regularly review logs for unusual file access patterns and unauthorized requests.

The due date for compliance with remediation steps is July 28, 2025.

Organizations failing to act risk data breaches, regulatory penalties, and reputational harm.

The Rails Action View path traversal vulnerability exemplifies the critical need for secure coding practices and timely vulnerability management.

Developers must remain vigilant, ensuring that user input is never trusted in file operations, and organizations should prioritize patching and compliance to defend against evolving threats.

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