How severe is CVE-2026-126209?

No CVSS score has been assigned to CVE-2026-126209 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-126209?

Affected package information for CVE-2026-126209 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-126209?

The records we use list no fixed release for CVE-2026-126209. Check the upstream advisory for a patched version, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2026-126209 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2026-126209 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-2026-126209 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-126209 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 type of vulnerability is CVE-2026-126209?

CVE-2026-126209 is classified as Cross-site Scripting (XSS) (CWE-79), CWE-184 (CWE-184). These weakness types 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-2026-126209 published, and has it been updated?

CVE-2026-126209 was published 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.

CVE-2026-126209: Flavorjones XSS

Description

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
The records we use list no fixed release for CVE-2026-126209. Check the upstream advisory for a patched version, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
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

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpret

O3 Security · Impact-Aware SCA

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CVE-2026-126209 — Flavorjones

Description

Detection & mitigation playbook

Detect

Remediation status

Mitigate without a patch

Frequently Asked Questions

Is CVE-2026-126209 in your dependencies?