CVE-2019-5136 in AWK-3131A
Summary
by MITRE
An exploitable privilege escalation vulnerability exists in the iw_console functionality of the Moxa AWK-3131A firmware version 1.13. A specially crafted menu selection string can cause an escape from the restricted console, resulting in system access as the root user. An attacker can send commands while authenticated as a low privilege user to trigger this vulnerability.
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Analysis
by VulDB Data Team • 04/02/2024
The CVE-2019-5136 vulnerability represents a critical privilege escalation flaw within the Moxa AWK-3131A industrial network device firmware version 1.13. This vulnerability specifically targets the iw_console functionality, which serves as a restricted console interface designed to limit administrative access to authorized users only. The flaw resides in how the system processes menu selection strings, creating a path where unprivileged users can potentially escape the intended security boundaries of the console environment. The vulnerability is particularly concerning in industrial control systems where network devices like the Moxa AWK-3131A serve as critical infrastructure components managing network communications and device access.
The technical implementation of this vulnerability stems from improper input validation within the console menu processing mechanism. When a low privilege authenticated user submits a specially crafted menu selection string, the system fails to properly sanitize or validate the input before processing it within the restricted console environment. This input validation failure creates a path for command injection or console escape sequences that bypass the intended access controls. The vulnerability operates through a classic buffer manipulation or command execution flaw where the system's parsing logic does not adequately distinguish between legitimate user inputs and maliciously crafted sequences designed to elevate privileges. This type of vulnerability aligns with CWE-20, which describes improper input validation, and CWE-78, which addresses OS command injection vulnerabilities.
The operational impact of this vulnerability extends beyond simple privilege escalation to represent a significant threat to industrial network security. An attacker exploiting this vulnerability can gain root-level access to the device, enabling complete control over the network infrastructure. This access allows for network reconnaissance, modification of device configurations, interception of network traffic, and potential lateral movement within the industrial control system. The implications are particularly severe in environments where these devices manage critical network operations, as the compromise of a single device can lead to widespread network disruption or unauthorized access to industrial processes. The vulnerability's exploitation requires only authenticated access as a low privilege user, making it particularly dangerous in environments where user access controls may be insufficient or where users have legitimate but limited access to network management functions.
Mitigation strategies for CVE-2019-5136 should focus on immediate firmware updates from Moxa, as the vendor has likely released patches addressing this specific vulnerability. Organizations should implement network segmentation to limit access to these devices and reduce the attack surface available to potential attackers. Access controls should be reviewed and strengthened to ensure that only authorized personnel have access to administrative functions, with principle of least privilege enforcement. Network monitoring should be enhanced to detect anomalous console access patterns or unusual command sequences that might indicate exploitation attempts. Additionally, regular security assessments of industrial control systems should include evaluation of console and administrative access mechanisms, as this vulnerability demonstrates the importance of proper input validation in restricted environments. The ATT&CK framework categorizes this type of vulnerability under privilege escalation techniques, specifically targeting T1068 which covers local privilege escalation through system binary manipulation or console escape sequences. Organizations should also consider implementing network access control lists and disabling unnecessary administrative services to reduce the likelihood of exploitation.