CVE-2026-33167: CVE-2026-33167: Cross-Site Scripting (XSS) in Ruby on Rails Action Pack Debug Exceptions

CVE-2026-33167: Cross-Site Scripting (XSS) in Ruby on Rails Action Pack Debug Exceptions Vulnerability ID: CVE-2026-33167 CVSS Score: 1.3 Published: 2026-03-23 Action Pack is a Rubygem for building web applications on the Rails framework. In versions on the 8.1 branch prior to 8.1.2.1, the debug exceptions page does not properly escape exception messages. A carefully crafted exception message could inject arbitrary HTML and JavaScript into the page, leading to Cross-Site Scripting (XSS). This affects applications with detailed exception pages enabled, which is the default in development environments. TL;DR Ruby on Rails Action Pack versions 8.1.0 through 8.1.2 contain a Cross-Site Scripting vulnerability in the debug exceptions page. Attackers can execute arbitrary JavaScript by reflecting crafted input into an unhandled exception message. ⚠️ Exploit Status: POC Technical Details CWE ID: CWE-79 Attack Vector: Network CVSS v4.0 Score: 1.3 Exploit Status: Proof of Concept CISA KEV: No Au