CVE-2021-45952 in Dnsmasq
Summary
by MITRE • 01/01/2022
Dnsmasq 2.86 has a heap-based buffer overflow in dhcp_reply (called from dhcp_packet and FuzzDhcp).
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Analysis
by VulDB Data Team • 08/04/2024
The heap-based buffer overflow vulnerability in Dnsmasq version 2.86 represents a critical security flaw that can be exploited to compromise network infrastructure devices relying on this DNS and DHCP server implementation. This vulnerability specifically affects the dhcp_reply function which is invoked from dhcp_packet and FuzzDhcp contexts, making it particularly dangerous in environments where Dnsmasq serves as a core network service component. The vulnerability arises from insufficient input validation and memory management when processing DHCP packets, creating opportunities for remote attackers to execute arbitrary code or cause denial of service conditions. The heap-based nature of this overflow indicates that malicious actors can manipulate heap memory structures to overwrite critical data or function pointers, potentially leading to complete system compromise.
The technical flaw stems from improper bounds checking within the DHCP reply processing logic where incoming packet data is copied into heap-allocated buffers without adequate validation of packet lengths or content boundaries. This allows attackers to craft specially malformed DHCP packets that exceed the allocated buffer size, resulting in memory corruption that can be leveraged for code execution. The vulnerability's exposure through multiple entry points including dhcp_packet and FuzzDhcp suggests that various network interactions could trigger the overflow condition, increasing the attack surface and exploitability. According to CWE classification, this represents a CWE-121 heap-based buffer overflow vulnerability, which falls under the broader category of memory safety issues that have historically been a primary vector for privilege escalation and remote code execution attacks. The ATT&CK framework would categorize this vulnerability under T1210 exploitation of remote services and T1068 local privilege escalation techniques, as successful exploitation could lead to full system compromise.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it enables potential remote code execution capabilities that could allow attackers to gain unauthorized access to network infrastructure. Organizations using Dnsmasq 2.86 in production environments face significant risk of network disruption, data breaches, and unauthorized access to critical network services. The vulnerability affects devices that rely on Dnsmasq for DHCP services, including routers, firewalls, and network appliances that implement this software stack. Attackers could exploit this flaw to redirect network traffic, intercept communications, or establish persistent access points within the network. The impact is particularly severe in enterprise environments where Dnsmasq is commonly deployed as part of network infrastructure, potentially allowing attackers to compromise entire network segments through a single vulnerable device.
Mitigation strategies should prioritize immediate patching of Dnsmasq installations to version 2.87 or later, which contains the necessary fixes for the heap-based buffer overflow. Network administrators should implement monitoring solutions to detect anomalous DHCP traffic patterns that could indicate exploitation attempts. Additional protective measures include implementing network segmentation to limit the impact of potential exploitation, deploying intrusion detection systems that can identify malformed DHCP packets, and establishing robust patch management processes to ensure timely updates across all network infrastructure components. Organizations should also consider implementing DHCP snooping and other network access controls to reduce the attack surface. The vulnerability highlights the importance of maintaining up-to-date network infrastructure software and demonstrates how seemingly routine network services can present critical security risks when vulnerable to memory corruption exploits. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other network services and prevent exploitation of similar memory safety flaws.