CVE-2026-18103
Received Received - Intake

Buffer Overflow in ISC DHCP Server via OMAPI Lease Request

Publication date: 2026-08-05

Last updated on: 2026-08-05

Assigner: Red Hat, Inc.

Description
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.

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Meta Information

Published
2026-08-05
Last Modified
2026-08-05
Generated
2026-08-05
AI Q&A
2026-08-05
EPSS Evaluated
N/A
NVD
CVE-2026-18103

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
red_hat dhcp_server *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-120 The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

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Executive Summary

This vulnerability is a buffer overflow flaw in the dhcp-server component. A remote attacker can exploit it by sending a specially crafted lease creation request with an overly long InfiniBand MAC address via the OMAPI port. This triggers a crash in the dhcpd service, causing a persistent denial of service (DoS) that requires manual intervention to resolve.

Detection Guidance

Check if the OMAPI port (7911) is exposed to untrusted networks. Inspect dhcpd logs for crashes or unusual lease creation requests. Look for entries with overly long InfiniBand MAC addresses in dhcpd.leases files.

Impact Analysis

If exploited, this vulnerability can crash the dhcpd service, making it unavailable until manually restarted. This disrupts network services relying on DHCP, potentially causing connectivity issues for devices. The attack requires network access to the OMAPI port but no additional credentials if TSIG authentication is not enabled.

Mitigation Strategies

Secure OMAPI access with TSIG key authentication. If already exploited, manually remove the problematic lease entry from /var/lib/dhcpd/dhcpd.leases and restart dhcpd.

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