CVE-2018-5732 in DHCP
Summary
by MITRE
Failure to properly bounds-check a buffer used for processing DHCP options allows a malicious server (or an entity masquerading as a server) to cause a buffer overflow (and resulting crash) in dhclient by sending a response containing a specially constructed options section. Affects ISC DHCP versions 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0
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Analysis
by VulDB Data Team • 07/17/2024
The vulnerability identified as CVE-2018-5732 represents a critical buffer overflow flaw within the ISC DHCP client implementation that affects multiple version ranges including 4.1.0 through 4.1-ESV-R15, 4.2.0 through 4.2.8, 4.3.0 through 4.3.6, and 4.4.0. This issue stems from inadequate bounds checking mechanisms when processing DHCP options within the dhclient component, creating a potential attack vector that can be exploited by malicious actors controlling DHCP servers or entities impersonating legitimate servers within a network environment.
The technical flaw manifests when the dhclient process receives a DHCP response containing specially crafted options data that exceeds the allocated buffer size. This failure to validate input boundaries allows an attacker to overflow the designated memory buffer, leading to unpredictable program behavior including application crashes and potential system instability. The vulnerability specifically targets the DHCP client's option processing functionality, where the client parses and handles various DHCP options sent by servers during the DHCP negotiation process. This represents a classic buffer overflow condition classified under CWE-121 as an insufficient bounds check during buffer copy operation, where the software fails to verify that the size of input data matches the size of the buffer allocated for storage.
The operational impact of this vulnerability extends beyond simple service disruption as it can be leveraged to cause denial of service against targeted systems running affected DHCP client versions. An attacker positioned within the network to intercept or manipulate DHCP communications can craft malicious responses that trigger the buffer overflow condition, resulting in dhclient process termination and subsequent network connectivity loss for affected clients. This vulnerability particularly affects environments where clients rely on automatic IP address assignment and configuration, making it a significant concern for enterprise networks, cloud deployments, and any infrastructure depending on DHCP for network management. The attack vector requires minimal privileges and can be executed through standard network communication protocols, making it particularly dangerous in environments where network access is not strictly controlled.
Mitigation strategies for CVE-2018-5732 primarily focus on upgrading to patched versions of ISC DHCP software, with affected versions receiving updates in subsequent releases. Network administrators should prioritize patch management to ensure all dhclient installations are updated to versions that properly implement bounds checking for DHCP option processing. Additional defensive measures include implementing network segmentation to limit exposure, monitoring DHCP traffic for anomalous option patterns, and deploying network access control measures to prevent unauthorized entities from acting as rogue DHCP servers. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation through service manipulation and denial of service attacks, specifically targeting the network infrastructure components that maintain client connectivity. Organizations should also consider implementing DHCP snooping features and DHCP server authentication mechanisms to further reduce the attack surface and prevent unauthorized DHCP server impersonation.