XSS in Rails

CVE-2026-126079

Action View is a framework for handling view template lookup and rendering and provides view helpers for building HTML. Prior to 8.1.4.1 and 8.0.5.2, with the HTML5 sanitizer (Rails::HTML5::Sanitizer, the default vendor on CRuby for applications using load_defaults 7.1 or later), Nokogiri before 1.19.5 serializes < and > unescaped inside attribute values. The Action View text helpers highlight and simple_format sanitize their input and then process the resulting HTML as a string: highlight splits it on tag boundaries to insert matches, and simple_format splits it into paragraphs on blank lines. An unescaped > or a blank line inside an attribute value could cause markup in that value, which the sanitizer left inert, to be emitted as live elements in the helper's html_safe output, possibly leading to XSS. Applications that use the HTML5 sanitizer and pass untrusted text to highlight, or to simple_format with html_options, are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Vulnerability class: XSS (Cross-Site Scripting)

Published .

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

  • Rails — versions < 8.0.5.2, >= 8.1, < 8.1.4.1

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-126079?
CVE-2026-126079 is a medium-severity vulnerability in Rails, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-11-10.
How severe is CVE-2026-126079?
Medium severity. CVSS v3 base score is 6.1 out of 10.