CVE-2026-18103

A flaw was found in dhcp-server. A remote attacker with network access to the OMAPI (Open Management Application Programming Interface) port, especially if not secured with TSIG (Transaction Signature) key authentication, could send a specially crafted lease creation request. This request, containing an overly long InfiniBand MAC address, triggers a buffer overflow in the print_hw_addr() function. Successful exploitation leads to a persistent denial of service (DoS), causing the dhcpd service to crash and preventing it from restarting without manual intervention.

This flaw has Moderate impact. A buffer overflow in the dhcpd service, exploitable via the OMAPI port (7911), can lead to a persistent denial of service. Exploitation requires network access to the OMAPI port, and if TSIG key authentication is not configured, no further credentials are needed. Successful exploitation crashes the dhcpd service, preventing its restart without manual intervention.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, secure OMAPI access by configuring TSIG key authentication to prevent unauthorized connections to the OMAPI port (7911). If the dhcpd service has already crashed due to this flaw, manually remove the problematic InfiniBand lease entry from /var/lib/dhcpd/dhcpd.leases and then restart the dhcpd service. Restarting the dhcpd service may temporarily interrupt DHCP services for clients.