CVE-2018-1158 in MikroTik
Summary
by MITRE
Mikrotik RouterOS before 6.42.7 and 6.40.9 is vulnerable to a stack exhaustion vulnerability. An authenticated remote attacker can crash the HTTP server via recursive parsing of JSON.
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Analysis
by VulDB Data Team • 03/17/2020
The vulnerability identified as CVE-2018-1158 affects Mikrotik RouterOS versions prior to 6.42.7 and 6.40.9, presenting a critical stack exhaustion flaw that enables authenticated remote attackers to cause HTTP server crashes. This vulnerability resides within the JSON parsing implementation of the RouterOS web interface, specifically targeting the HTTP server component that handles JSON data structures. The flaw manifests when the system processes malformed or recursively structured JSON input, leading to excessive stack memory consumption that ultimately results in system instability and service disruption. The vulnerability is particularly concerning as it requires only authentication to exploit, meaning that an attacker with valid credentials can trigger the denial of service condition without requiring additional privileges or complex attack vectors.
The technical implementation of this vulnerability stems from insufficient bounds checking and recursive parsing logic within the JSON parser component of Mikrotik's HTTP server. When processing JSON data containing deeply nested or recursive structures, the parser consumes stack memory in a manner that grows exponentially with input complexity. This behavior directly maps to CWE-770, which describes the allocation of resources without proper limits or checks, and aligns with ATT&CK technique T1499.004 for network denial of service attacks. The stack exhaustion occurs because the recursive parsing mechanism does not implement proper depth limiting or memory allocation constraints, allowing attackers to craft malicious JSON payloads that cause the stack to overflow and subsequently crash the HTTP server process. The vulnerability affects the web management interface, which is commonly used by network administrators to configure and monitor router settings, making it a particularly attractive target for attackers seeking to disrupt network operations.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise network availability and administrative access to Mikrotik devices. Network administrators who rely on the web interface for routine maintenance and configuration tasks may find their systems rendered inaccessible during an attack, potentially leading to extended downtime and operational disruption. The vulnerability affects both the web-based management interface and any services that depend on the HTTP server for communication, creating cascading effects throughout the network infrastructure. Attackers can exploit this flaw to repeatedly crash the HTTP server, forcing administrators to restart services manually or perform system recovery operations. The ease of exploitation, combined with the critical nature of the affected service, makes this vulnerability particularly dangerous in enterprise environments where network uptime is crucial for business operations.
Mitigation strategies for CVE-2018-1158 primarily involve applying the vendor-provided security patches that address the stack exhaustion issue in the JSON parsing implementation. Mikrotik released updates in versions 6.42.7 and 6.40.9 that introduce proper bounds checking and recursive depth limitations within the JSON parser. Organizations should immediately upgrade their RouterOS installations to these patched versions to eliminate the vulnerability. Network segmentation and access control measures can provide additional defense-in-depth, limiting the scope of potential attacks by restricting access to the web management interface to trusted administrative networks. Implementing monitoring solutions that detect unusual HTTP server behavior or repeated connection failures can help identify exploitation attempts. Security teams should also consider disabling unnecessary web management services when not actively required, reducing the attack surface for this type of vulnerability. Regular vulnerability assessments and penetration testing should be conducted to identify similar issues in other network components, while maintaining updated security baselines that align with industry standards such as those defined by the Center for Internet Security and NIST guidelines for network device security hardening.