CVE-2021-21890 in PremierWave
Summary
by MITRE • 12/22/2021
A stack-based buffer overflow vulnerability exists in the Web Manager FsBrowseClean functionality of Lantronix PremierWave 2050 8.9.0.0R4 (in QEMU). A specially crafted HTTP request can lead to remote code execution in the vulnerable portion of the branch (deletedir). An attacker can make an authenticated HTTP request to trigger this vulnerability.
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Analysis
by VulDB Data Team • 12/26/2021
The vulnerability identified as CVE-2021-21890 represents a critical stack-based buffer overflow within the Web Manager FsBrowseClean functionality of Lantronix PremierWave 2050 version 8.9.0.0R4 running in QEMU virtualization environment. This flaw resides in the deletedir branch of the file system browsing component, where improper input validation allows malicious data to overwrite adjacent stack memory regions. The vulnerability manifests when the system processes HTTP requests containing specially crafted parameters that exceed the allocated buffer space, creating conditions for arbitrary code execution. The attack vector requires authentication, meaning an attacker must first establish valid credentials to exploit the vulnerability, though this authentication requirement does not mitigate the severity of the potential compromise.
The technical implementation of this buffer overflow stems from inadequate bounds checking within the file system management routines of the embedded web interface. When processing directory deletion requests, the system fails to properly validate the length of input parameters before copying them into fixed-size stack buffers. This classic programming error creates a predictable memory corruption scenario where attacker-controlled data can overwrite return addresses, function pointers, and other critical stack variables. The CWE-121 classification applies directly to this vulnerability as it represents a stack-based buffer overflow where insufficient boundary checks allow data to overwrite adjacent memory locations. The specific nature of the flaw allows for precise memory corruption that can be leveraged to redirect program execution flow.
From an operational perspective, this vulnerability presents a significant risk to network infrastructure devices running the affected Lantronix firmware version. The remote code execution capability means that authenticated attackers can potentially gain full control over the device's operating system, enabling them to install malicious software, modify configurations, access sensitive data, or establish persistent backdoors. The QEMU environment suggests this vulnerability may be exploitable in virtualized deployments, expanding the potential attack surface beyond physical hardware installations. The impact extends beyond individual device compromise as the PremierWave 2050 serves as a network gateway device, potentially allowing attackers to use compromised units as launching points for broader network infiltration. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as successful exploitation would enable command execution within the device's operating environment.
Mitigation strategies for CVE-2021-21890 should prioritize immediate firmware updates from Lantronix to address the underlying buffer overflow conditions. Network administrators must implement strict access controls and monitor authentication attempts for suspicious activity patterns that may indicate exploitation attempts. The principle of least privilege should be enforced by limiting administrative access to the web interface to authorized personnel only, while implementing multi-factor authentication where possible. Network segmentation can help contain potential compromises by isolating the affected devices from critical network segments. Security monitoring solutions should be configured to detect anomalous HTTP request patterns and unusual file system operations that might indicate exploitation attempts. Additionally, implementing network-based intrusion detection systems with signatures for this specific vulnerability can provide early warning of attempted exploitation. Regular vulnerability assessments and penetration testing should be conducted to identify similar buffer overflow conditions in other network infrastructure components, particularly those with web-based management interfaces that may be susceptible to similar flaws.