FreeBSD-SA-20:26.dhclient : dhclient heap overflow
Versions Affected : All verisons prior to FreeNAS 11.3-U5
dhclient(8) is the default IPv4 DHCP client used on FreeBSD. It is responsible for contacting DHCP servers on a network segment, and for initializing and configuring network interfaces and configuring name resolution based on received information.
dhclient(8) handles DHCP option 119, the Domain Search Option, which provides a list of domains to search when resolving names using DNS. The option data format uses a compression scheme to avoid transmitting duplicate domain name labels. When parsing option 119 data, dhclient(8) computes the uncompressed domain list length so that it can allocate an appropriately sized buffer to store the uncompressed list. The code to compute the length failed to handle certain malformed input, resulting in a heap overflow when the uncompressed list is copied into in inadequately sized buffer.
No workaround is available.
- Upgrade to FreeNAS 11.3-U5 or later.