sanitize-html CVE-2026-113657

Exploitation requires a non-default sanitize-html configuration that explicitly permits namespace-prefixed SVG animation elements (e.g. prefixed <animate>/<set>-style tags) together with the relevant URL-targeting attributes; the description states the default sanitizer configuration is not unconditionally affected. A second hard limit is user interaction (UI:R): the injected SVG only rewrites a link destination to an unsafe URI, and script execution occurs only when a victim actually activates (clicks) that link. The attacker also needs the ability to submit HTML/SVG content that passes through the sanitizer (PR:L in the vector). These stacked prerequisites - non-default allow-list, content-submission access, and victim click - substantially constrain realistic exploitation.

This is a genuinely low-priority issue, and the signals are internally consistent rather than conflicting. The CVSS 3.1 base score of 3.7 (Low) reflects a hard-to-exploit XSS: AV:N (web-delivered content) but AC:H (requires a non-default sanitizer configuration), PR:L (an authenticated/content-submitting actor), UI:R (a victim must activate the malicious link), S:U, and only C:L/I:L/A:N impact. No EPSS probability was supplied in the input, so exploitation likelihood cannot be quantified from this data. The vulnerability is NOT on the CISA KEV list and no POC/exploit code is referenced, so there is no public exploit identified at time of analysis. The combined picture - low technical impact, two independent limiting conditions (non-default config AND user interaction), and no evidence of exploitation - means this is a defense-in-depth fix rather than an urgent patch priority. The one caveat is reach: sanitize-html is an extremely widely depended-upon npm sanitizer, so while any single deployment is low-risk, the affected library's footprint is large; teams running the vulnerable 2.17.7-2.17.x range with the specific SVG-animation allowances enabled should still patch to 2.18.0.

In an ApostropheCMS/sanitize-html deployment whose configuration has been customized to permit namespace-prefixed SVG animation elements and their URL-targeting attributes, an attacker with the ability to submit content crafts an SVG whose prefixed animation tag evades the unprefixed SMIL animation-element check. The sanitizer passes it through, and after rendering the animation rewrites a link's destination to an unsafe (e.g. javascript:) URI, so script executes when a victim clicks the affected link. No public exploit code is referenced in the available data.