CVE-2024-42040 is a buffer overflow vulnerability identified in the net/bootp.c source file of DENEX U-Boot, a widely used open-source bootloader for embedded systems. This vulnerability has existed since the initial commit of the codebase in 2002 and persists across all platforms running this U-Boot version. The flaw arises from improper handling of DHCP responses, specifically in the processing of DHCP-provided parameters. An attacker positioned on the same local network can craft malicious DHCP responses that trigger a buffer overflow, causing the system to leak between 4 and 32 bytes of memory located beyond the intended packet boundaries. The amount of leaked memory depends on how the DHCP parameters are subsequently used. The vulnerability is classified under CWE-120 (Classic Buffer Overflow), indicating a failure to properly validate input sizes before copying data. The CVSS v3.1 base score is 8.1, reflecting high severity due to the attack vector requiring only local network access (AV:A), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact includes high confidentiality loss (C:H) and high availability impact (A:H), but no integrity impact (I:N). Although no public patches or known exploits are currently available, the long-standing presence of this vulnerability in a critical bootloader component makes it a significant concern for embedded device security. Exploitation could allow attackers to glean sensitive memory contents, potentially exposing cryptographic keys, credentials, or other sensitive data, and cause denial of service by destabilizing the boot process.

The vulnerability poses a substantial risk to organizations deploying embedded devices that utilize DENEX U-Boot as their bootloader, including IoT devices, industrial control systems, networking equipment, and other embedded platforms. Memory disclosure can lead to leakage of sensitive information such as cryptographic keys, configuration data, or credentials, which attackers could leverage for further compromise or lateral movement. The denial of service impact could disrupt device availability, affecting critical infrastructure or business operations. Since exploitation requires only local network access, attackers who gain proximity or network access (e.g., via compromised devices or insider threats) can exploit this vulnerability without authentication or user interaction. This increases the risk in environments with shared or untrusted local networks. The broad platform coverage of the vulnerability means a wide range of devices are potentially affected, amplifying the threat surface. The absence of known exploits in the wild currently reduces immediate risk but does not diminish the urgency for remediation given the vulnerability’s age and severity.

To mitigate CVE-2024-42040, organizations should first identify all devices running DENEX U-Boot and assess their exposure to local network threats. Since no official patches are currently available, organizations should monitor vendor advisories for updates or patches addressing this vulnerability. In the interim, network segmentation should be enforced to isolate vulnerable embedded devices from untrusted or less secure network segments, limiting attacker access to the local network. Employ DHCP snooping and filtering on switches to block unauthorized or malicious DHCP responses that could exploit this vulnerability. Where feasible, replace or upgrade affected devices with versions of U-Boot that have been audited and patched to fix this buffer overflow. Implement strict network access controls and continuous monitoring to detect anomalous DHCP traffic patterns indicative of exploitation attempts. Additionally, consider deploying host-based intrusion detection systems on devices capable of supporting them to detect abnormal behavior during boot or network interactions. Finally, maintain an inventory of embedded devices and incorporate bootloader security into regular vulnerability management and patching cycles.