{"id":"CVE-2026-18103","title":"Dhcp-server: dhcp-server: persistent denial of service due to buffer overflow via omapi","summary":"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 sp…","severity":"medium","cvss":4.9,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H","cvssSource":"cna","cwe":["CWE-120"],"vendor":"Red Hat","product":"dhcp","affected":["dhcp (all versions)","dhcp (all versions)","dhcp (all versions)","dhcp (all versions)"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-08-05T13:58:45.550060Z"},"published":"2026-08-04","updated":"2026-11-06","sourceUpdated":"2026-11-06T18:08:49.111Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-18103","references":[{"url":"https://access.redhat.com/security/cve/CVE-2026-18103"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2508081","label":"RHBZ#2508081"}],"tags":["cve.org"],"epss":0.00709,"epssPercentile":0.53738,"ingestedAt":"2026-11-06T19:01:36.641Z","slug":"CVE-2026-18103","body":"## Overview\n\nA 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.\n\n## Affected\n\n- `dhcp (all versions)`\n- `dhcp (all versions)`\n- `dhcp (all versions)`\n- `dhcp (all versions)`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n### Workarounds\n\nTo 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.","depth":"sunlit","depthScore":27,"depthScoreParts":{"impact":27,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}