PHP ext/standard/var_unserializer.c NULL Pointer Dereference Denial of Service Vulnerability [CVE-2018-19396]

CVE Number – CVE-2018-19396

A vulnerability in PHP could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.The vulnerability is due to a NULL pointer dereference condition that exists in the ext/standard/var_unserializer.c file of the affected software when an unserialize call is made for the com, dotnet, or variant class. An attacker could exploit this vulnerability by sending a request that submits malicious input to the affected software. A successful exploit could trigger a NULL pointer dereference condition, which the attacker could use to cause the software to crash, resulting in a DoS condition.Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available.PHP has confirmed the vulnerability and released software updates.

Analysis

• To exploit this vulnerability, the attacker must send a malicious request to the targeted system, making exploitation more difficult in environments that restrict network access from untrusted sources.

Safeguards

• Administrators are advised to allow only trusted users to have network access.Administrators are advised to run both firewall and antivirus applications to minimize the potential of inbound and outbound threats.Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.Administrators can help protect affected systems from external attacks by using a solid firewall strategy.Administrators are advised to monitor affected systems.

Vendor Announcements

• PHP has confirmed the vulnerability at the following link: Bug #77177

Fixed Software

• PHP released software updates at the following link: PHP Downloads