External Control of System or Configuration Setting Affecting phenx/php-svg-lib package, versions <0.5.1
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PHP-PHENXPHPSVGLIB-6125684
- published14 Dec 2023
- disclosed12 Dec 2023
- creditcod3beat
Introduced: 12 Dec 2023
CVE-2023-50252 (opens in a new tab)How to fix?
Upgrade phenx/php-svg-lib to version 0.5.1 or higher.
Overview
phenx/php-svg-lib is a library to read, parse and export to PDF SVG files.
Affected versions of this package are vulnerable to External Control of System or Configuration Setting due to improper sanitization of the href attribute from the <use> tag when it is merged with an <image> tag. An attacker can cause an unsafe file read that may lead to PHAR Deserialization vulnerability in PHP versions prior to 8 by manipulating the href attribute.
Workaround
Systems utilizing php-svg-lib can implement input validation using logic similar to the following:
$parser = xml_parser_create("utf-8"); xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, false); xml_set_element_handler( $parser, function ($parser, $name, $attributes) { if (strtolower($name) === "image" || strtolower($name) === "use") { $attributes = array_change_key_case($attributes, CASE_LOWER); $urls = []; $urls[] = $attributes["xlink:href"] ?? ""; $urls[] = $attributes["href"] ?? ""; foreach ($urls as $url) { if (!empty($url)) { // perform validation here } } }// include other tag/attribute validation }, false);
if (($fp = fopen($url, "r")) !== false) { while ($line = fread($fp, 8192)) { xml_parse($parser, $line, false); } fclose($fp); xml_parse($parser, "", true); } xml_parser_free($parser);
PoC
<svg width="200" height="200"
xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<image id="phar:///poc.phar" xlink:href="file:///existing/safe/image.png" />
<use href="phar:///poc.phar" width="500" height="500"/>
</svg>