CVE-2021-21891 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 (deletefile). 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 CVE-2021-21891 vulnerability represents a critical stack-based buffer overflow within the Lantronix PremierWave 2050 device firmware version 8.9.0.0R4 running in QEMU emulation environment. This vulnerability specifically targets the Web Manager FsBrowseClean functionality, which handles file system operations through the HTTP interface. The flaw exists in the deletefile branch of the code execution path, making it particularly dangerous as it allows for arbitrary code execution when exploited. The vulnerability requires authentication to trigger, meaning an attacker must first establish valid credentials to access the web management interface before attempting exploitation.
The technical implementation of this buffer overflow occurs due to insufficient input validation and bounds checking within the file deletion function. When processing HTTP requests containing specially crafted parameters, the application fails to properly validate the length of user-supplied data before copying it into fixed-size stack buffers. This classic programming error creates a condition where malicious input can overwrite adjacent memory locations, potentially corrupting the stack frame and allowing an attacker to manipulate program execution flow. The vulnerability manifests specifically during the processing of file deletion requests through the web interface, where the application does not enforce proper buffer size limits on incoming data.
Operationally, this vulnerability presents a severe risk to network infrastructure security as it enables remote code execution with authenticated access. An attacker who gains valid login credentials can exploit this flaw to execute arbitrary code on the target device, potentially leading to complete system compromise. The impact extends beyond simple privilege escalation as the attacker could gain access to sensitive network configurations, modify device settings, or establish persistent backdoors. The QEMU environment aspect suggests this vulnerability may also affect similar virtualized deployments or development environments where the same firmware version is used, broadening the potential attack surface.
Mitigation strategies for CVE-2021-21891 should focus on immediate firmware updates from Lantronix to address the identified buffer overflow vulnerability. Organizations should also implement network segmentation to limit access to the web management interface, enforce strong authentication mechanisms including multi-factor authentication, and monitor network traffic for suspicious HTTP requests containing malformed parameters. The vulnerability aligns with CWE-121 stack-based buffer overflow classification and represents a technique commonly associated with the ATT&CK tactic of Execution, specifically through the use of remote code execution capabilities. Regular security assessments and input validation reviews should be conducted to prevent similar issues in other components of the system, while network monitoring solutions should be configured to detect anomalous patterns in web requests that might indicate exploitation attempts.