# CVE-2026-126205: Loofah: Regular expression denial of service in the SVG local-reference check

Status: published. Published: 2026-11-12. Updated: 2026-11-12.

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. Prior to 2.25.3, the Loofah HTML5 sanitizer checks href and xlink:href on elements in SVG_ALLOW_LOCAL_HREF with a regular expression whose line anchor and newline-matching whitespace cause an all-whitespace value to be rescanned from every line start. An attacker can submit an SVG reference element with a long multiline-whitespace attribute and consume CPU quadratically during sanitization. CRuby 3.1 and earlier and JRuby are affected, while CRuby 3.2 and later uses linear-time regular-expression matching. The default safelist reaches the vulnerable check without a configuration change. This issue is fixed in version 2.25.3.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- flavorjones / loofah: < 2.25.3 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-400, CWE-1333

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/flavorjones/loofah/security/advisories/GHSA-mf2j-8f84-cc9q (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/flavorjones/loofah/pull/324 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/flavorjones/loofah/commit/2f31e7fae36036c9882d3d0fae720e1014c57cd1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/flavorjones/loofah/releases/tag/v2.25.3 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-126205; retrieved 2026-11-12; source updated 2026-11-12

Revision: 0591bc6dbe9afcbaf91c47a1b1affdd9d678cce70852c91686e2018fe8988e75

Canonical: https://y2.dev/cve/CVE-2026-126205

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