CVE-2025-12198 is a heap-based buffer overflow vulnerability identified in the dnsmasq software, specifically affecting versions 2.73rc1 through 2.73rc6. The flaw resides in the parse_hex function within the src/util.c file, part of the Config File Handler component. The vulnerability arises due to improper handling and manipulation of the argument 'i', which leads to a heap-based buffer overflow condition. This memory corruption can be exploited to overwrite adjacent memory, potentially allowing an attacker to execute arbitrary code or cause a denial of service by crashing the service. The attack vector requires local access with low privileges (PR:L), no user interaction (UI:N), and low attack complexity (AC:L). The CVSS 4.0 base score is 8.5, indicating high severity, with high impact on confidentiality, integrity, and availability. The exploit has been publicly disclosed, increasing the risk of exploitation, although no confirmed exploits in the wild have been reported yet. The vendor has not issued a patch or responded to the disclosure, leaving affected systems exposed. dnsmasq is widely used as a lightweight DNS forwarder and DHCP server in various network devices, including routers, embedded systems, and Linux distributions, making this vulnerability relevant to a broad range of environments. The lack of authentication requirement and the local access prerequisite suggest that attackers need some foothold on the system to leverage this vulnerability, such as through compromised user accounts or local access vectors.

For European organizations, the impact of CVE-2025-12198 can be significant, especially for those relying on dnsmasq in network infrastructure, embedded devices, or internal DNS/DHCP services. Successful exploitation could lead to local privilege escalation, allowing attackers to gain higher system privileges, execute arbitrary code, or disrupt network services by causing crashes. This can compromise confidentiality and integrity of network communications and availability of critical network services. Organizations in sectors such as telecommunications, government, finance, and critical infrastructure are particularly at risk due to their reliance on stable and secure network services. The local access requirement limits remote exploitation but does not eliminate risk, as attackers with initial access or insider threats could leverage this vulnerability. The absence of vendor response and patches increases exposure time, potentially allowing attackers to develop and deploy exploits targeting vulnerable European systems. Additionally, embedded devices with dnsmasq are often less frequently updated, increasing the attack surface.

Until an official patch is released, European organizations should implement strict local access controls to limit user privileges and prevent unauthorized local access to systems running vulnerable dnsmasq versions. Employing application whitelisting and monitoring for unusual process behavior or crashes related to dnsmasq can help detect exploitation attempts. Network segmentation should be enforced to isolate critical infrastructure and reduce lateral movement opportunities. Organizations should inventory all devices running dnsmasq to identify vulnerable versions and prioritize remediation. Where possible, upgrade dnsmasq to a non-vulnerable version or apply vendor-provided mitigations once available. Consider deploying host-based intrusion detection systems (HIDS) to monitor for heap corruption indicators. For embedded devices, coordinate with vendors or consider device replacement if patches are not forthcoming. Regularly review and tighten access policies to minimize the risk of local exploitation. Finally, maintain awareness of threat intelligence updates regarding exploit availability and adjust defenses accordingly.