How severe is CVE-2026-126079?

CVE-2026-126079 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-126079?

CVE-2026-126079 affects the following packages: actionview (RubyGems), actionview (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2026-126079?

Update actionview to 8.1.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-126079 is resolved across your whole dependency graph.

How do I detect CVE-2026-126079 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for actionview, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-126079 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2026-126079 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-126079 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-126079?

CVE-2026-126079 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 28th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-126079?

CVE-2026-126079 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-126079 published, and has it been updated?

CVE-2026-126079 was published on November 10, 2026 and was last updated on November 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2026-126079 — actionview

MEDIUMFix: rails/rails@adc3a32

CVE-2026-126079 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in actionview. A fix is available for actionview — see the affected versions and patch details below.

Action View: Possible XSS vulnerability in Action View text helpers

Also known asGHSA-2p2f-4rq4-gjwc

Published

Nov 10, 2026

Updated

Nov 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

💎actionview💎actionview

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Impact

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.

Details

The fixed releases require rails-html-sanitizer 1.7.2 or later, which requires Loofah 2.25.3 and Nokogiri 1.19.5. With these versions, the HTML5 sanitizer escapes < and > in attribute values as < and >, as the HTML4 sanitizer already does. The parsed DOM is unchanged, but code or tests that compare sanitized HTML as a string may see the new serialization.

Workarounds

Upgrade Nokogiri to 1.19.5 or later; the escaping is in its HTML5 serializer, so no Rails upgrade is needed. Alternatively, use the HTML4 sanitizer by setting config.action_view.sanitizer_vendor = Rails::HTML4::Sanitizer.

Releases

The fixed releases are available at the normal locations.

Patches for those who cannot upgrade at once:

Credit

This issue was responsibly reported by HackerOne researcher azaran. This issue was also found by the Anthropic OSS Scanner (ANT-2026-RTK47OH0).

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`actionview`	≥ 8.1.0.beta1&&< 8.1.4.1	8.1.4.1`bundle update actionview --conservative`
💎RubyGems	`actionview`	all versions	8.0.5.2`bundle update actionview --conservative`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for actionview, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update actionview to 8.1.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-126079 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact 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 ine