How severe is CVE-2026-126078?

CVE-2026-126078 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-2026-126078?

CVE-2026-126078 affects the following packages: actionview (RubyGems), actionview (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2026-126078?

Update actionview to 8.1.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-126078 is resolved across your whole dependency graph.

How do I detect CVE-2026-126078 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-2026-126078 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-2026-126078 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-126078 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-2026-126078?

CVE-2026-126078 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-2026-126078?

CVE-2026-126078 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-2026-126078 published, and has it been updated?

CVE-2026-126078 was published on November 10, 2026 and was last updated on November 14, 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-2026-126078 — actionview

MEDIUMFix: rails/rails@0693819

CVE-2026-126078 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 highlight helper

Also known asGHSA-v6rj-xm57-3p59

Published

Nov 10, 2026

Updated

Nov 14, 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

ActionView::Helpers::TextHelper#highlight substitutes each matched phrase into the :highlighter string without escaping it and returns the result marked HTML-safe. Because sanitizing leaves quote characters in text unescaped, a match substituted into a quoted attribute value of the highlighter, such as the <a href="search?q=\1"> form shown in the method's documentation, could end the attribute value and add attributes to the element, possibly leading to XSS. Applications are affected when they pass a :highlighter that places a placeholder inside an attribute value and highlight text or phrases that a user controls. The default <mark>\1</mark> highlighter and the block form are not affected.

Details

The fixed releases HTML-escape each group substituted into the :highlighter string, so quotes in a match are rendered as " and '. Only the numbered placeholders \0 to \9 are expanded; other String#sub replacement escapes, such as \k<name>, \& and \\, are left as written. A match can no longer begin on the > that closes a preceding tag. Escaping makes a placeholder safe as element content or inside a quoted attribute value, but not in an unquoted attribute value, a URL, JavaScript or CSS context, or an attribute whose value is HTML. See the Action View CHANGELOG for details.

Workarounds

Use a :highlighter that places the matched phrase only in element content, such as the default <mark>\1</mark>.

Releases

The fixed releases are available at the normal locations.

Patches for those who cannot upgrade at once:

Credit

This issue was found by the Anthropic OSS Scanner (ANT-2026-THHUJQVO).

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-2026-126078 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 `ActionView::Helpers::TextHelper#highlight` substitutes each matched phrase into the `:highlighter` string without escaping it and returns the result marked HTML-safe. Because sanitizing leaves quote characters in text unescaped, a match substituted into a quoted attribute value of the highlighter, such as the `<a href="search?q=\1">` form shown in the method's documentation, could end the attribute value and add attributes to the element, possibly leading to XSS. Applications are affected when they pass a `:highlighter` that places a placeholder inside an attribute value and highli