CVE-2026-49481 in UpSnap
Summary
by MITRE • 08/13/2026
UpSnap is a wake on lan web app. Versions prior to 5.4.0 have an OS command injection vulnerability in the UpSnap’s device management functionality due to the presence of unsafe shell command template interpolation using the ip and the mac fields. User-controlled values can be inserted into the wake_cmd and shutdown_cmd templates and executed via /bin/sh -c (Linux) or cmd /C (Windows) without sanitization, resulting in an authenticated Remote Code Execution (RCE). A low-privileged user with permission to create or edit devices can execute arbitrary operating system commands on the UpSnap hosted server. Version 5.4.0 patches the issue.
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Analysis
by VulDB Data Team • 08/13/2026
The UpSnap web application presents a critical security vulnerability through its device management functionality, where unauthorized command execution becomes possible due to improper input validation and sanitization practices. This vulnerability specifically affects versions prior to 5.4.0 and stems from unsafe shell command template interpolation that occurs when processing user-supplied data in ip and mac fields. The flaw manifests in the way the application constructs system commands by directly incorporating user-controllable values into shell execution templates without proper sanitization or parameterization, creating an environment where malicious input can be interpreted as executable commands rather than benign data.
The technical implementation of this vulnerability aligns with common command injection patterns that fall under CWE-78, which describes improper neutralization of special elements used in OS commands. The application's use of shell command templates for wake_on_lan and shutdown operations creates a direct pathway for attackers to inject malicious payloads through the device management interface. When users with appropriate permissions attempt to create or modify device entries, they can insert specially crafted input into the ip and mac fields that gets interpolated directly into system command strings. These commands are then executed through shell interpreters without any sanitization, allowing complete control over the underlying operating system.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables authenticated remote code execution on the UpSnap server itself. A low-privileged user who possesses permissions to create or edit devices can leverage this flaw to execute arbitrary commands with the privileges of the web application service account, potentially leading to complete system compromise. This scenario represents a significant risk in environments where the UpSnap application runs with elevated privileges or has access to sensitive network resources. The vulnerability essentially transforms a legitimate device management feature into a weaponized attack vector that can be exploited by users who should normally have limited access rights.
The mitigation strategy for this vulnerability involves implementing proper input validation and sanitization techniques along with parameterized command execution methods. Version 5.4.0 addresses this issue through proper sanitization of user inputs before they are incorporated into shell commands, ensuring that special characters and command delimiters cannot be interpreted by the shell interpreter. Organizations should also consider implementing additional security controls such as principle of least privilege enforcement for device management permissions, input validation at multiple layers within the application architecture, and regular security testing to identify similar patterns in other system components. The fix demonstrates the importance of proper command construction practices that prevent the injection of malicious code through user-controllable inputs.
This vulnerability type aligns with ATT&CK technique T1059 which covers the execution of system commands and scripts, and specifically relates to the use of shell commands for privilege escalation and lateral movement within compromised systems. The attack surface is particularly concerning as it requires minimal privileges to exploit, making it attractive to attackers who may have gained access through other means but need to escalate their capabilities within the network environment. Security practitioners should monitor for exploitation attempts through logs related to device management activities and implement proper network segmentation to limit the potential impact of successful exploitation attempts. The vulnerability underscores the critical importance of secure coding practices in web applications that interact with system-level functionality, particularly when dealing with user-supplied data that may be processed through shell interpreters.