CVE-2015-6838: PHP

High severity, CVSS 7.5. EPSS: 8.1% chance of exploitation in the next 30 days.

The xsl_ext_function_php function in ext/xsl/xsltprocessor.c in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13, when libxml2 before 2.9.2 is used, does not consider the possibility of a NULL valuePop return value before proceeding with a free operation after the principal argument loop, which allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted XML document, a different vulnerability than CVE-2015-6837.

Affected products

• PHP PHP: version 5.6.0 only; version 5.6.1 only; version 5.6.2 only; version 5.6.3 only; version 5.6.4 only; version 5.6.5 only; …
• Xmlsoft LIBXML2: up to and including 2.9.1

Published 2016-05-16. Last modified 2026-06-17.