CVE-2018-5951 in MikroTik
Summary
by MITRE
An issue was discovered in Mikrotik RouterOS. Crafting a packet that has a size of 1 byte and sending it to an IPv6 address of a RouterOS box with IP Protocol 97 will cause RouterOS to reboot imminently. All versions of RouterOS that supports EoIPv6 are vulnerable to this attack.
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Analysis
by VulDB Data Team • 04/09/2024
This vulnerability in Mikrotik RouterOS represents a critical remote code execution flaw that exploits a buffer overflow condition in the IPv6 handling mechanism. The issue specifically affects systems running RouterOS versions that support Encapsulation over IPv6 (EoIPv6) functionality, where the device fails to properly validate incoming packet sizes before processing them. When an attacker crafts a malformed packet with exactly one byte of data and targets an IPv6 address configured on the RouterOS device using IP Protocol 97, the system immediately crashes and reboots without any opportunity for graceful shutdown or error handling. This type of vulnerability falls under CWE-121, which describes buffer overflow conditions where insufficient bounds checking allows malicious data to overwrite adjacent memory locations.
The technical exploitation of this vulnerability demonstrates a fundamental flaw in input validation and memory management within the RouterOS networking stack. IP Protocol 97 corresponds to the PIM (Protocol Independent Multicast) protocol, and the attack leverages the fact that RouterOS does not properly validate the packet size when processing PIM messages over IPv6. The one-byte packet size is insufficient to contain valid PIM protocol data structures, yet the router's processing logic does not perform adequate bounds checking before attempting to parse the malformed data. This creates a classic stack-based buffer overflow scenario where the minimal packet size triggers an immediate memory corruption event that results in system termination. The vulnerability affects all RouterOS versions that implement EoIPv6 functionality, making it particularly concerning for network infrastructure devices that are often deployed in critical environments.
The operational impact of this vulnerability extends beyond simple service disruption to represent a potential denial of service attack vector that could be exploited by malicious actors to target network infrastructure. Network administrators and security teams face the challenge of identifying vulnerable devices across their network infrastructure, as the attack can be executed remotely without authentication requirements. The immediate reboot behavior provides no opportunity for incident response teams to gather forensic data or implement temporary mitigations, making this particularly dangerous in mission-critical environments. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a significant risk to network availability and business continuity. Organizations using Mikrotik devices in their network infrastructure must consider the potential for cascading failures if multiple devices in a network are vulnerable to the same attack vector.
The remediation approach for this vulnerability requires immediate patching of all affected RouterOS versions through official Mikrotik firmware updates. Organizations should also implement network segmentation and access control measures to limit exposure of vulnerable devices to untrusted networks. Network monitoring should be enhanced to detect unusual reboot patterns or malformed packet traffic targeting IPv6 addresses. Additionally, administrators should consider disabling EoIPv6 functionality on devices where it is not strictly required, as this removes the attack surface entirely. The vulnerability highlights the importance of robust input validation and memory safety practices in network infrastructure software, particularly in embedded systems where resource constraints may lead to insufficient defensive programming. Regular vulnerability assessments and security audits should be conducted to identify similar issues in other network equipment and firmware implementations.