CVE-2026-71243 in backmeup
Summary
by MITRE • 08/05/2026
The backmeup npm package assembles shell command strings by directly concatenating its option values (name, source, destination, filter) - e.g. cmd = "mkdir -p " + path.join(info.destination, info.name) + "; " - and executes the resulting string through a shell via ssh2-exec (locally via child_process, or remotely via SSH when an ssh handle is supplied), rather than using execFile/spawn with an argument array. The only processing applied is path.normalize()/path.join(), which do not neutralize shell metacharacters (;, |, &, $(), backticks, newline). Any application that passes attacker-influenced values into these options (e.g. a user-chosen backup name) is vulnerable to arbitrary OS command execution on the backup host, or on the remote SSH target when one is configured.
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Analysis
by VulDB Data Team • 08/06/2026
The backmeup npm package contains a critical command injection vulnerability stemming from improper shell command construction and execution practices. This vulnerability arises from the package's direct concatenation of user-supplied option values into shell command strings without adequate sanitization or escaping mechanisms. The flaw manifests when the package constructs commands such as cmd = "mkdir -p " + path.join(info.destination, info.name) + "; " where attacker-controlled data flows directly into the command execution pipeline. The vulnerability is particularly dangerous because it leverages shell metacharacters including semicolons, pipes, ampersands, command substitution parentheses, backticks, and newlines that can be exploited to inject additional commands into the executed shell string.
The technical implementation of this vulnerability follows a classic insecure command construction pattern where path.join() and path.normalize() functions are used solely for path manipulation without considering shell escaping requirements. These path manipulation functions do not perform shell metacharacter neutralization, leaving the system susceptible to arbitrary code execution when attacker-influenced data enters through any of the package options including name, source, destination, or filter parameters. The vulnerability is exacerbated by the package's use of ssh2-exec for remote execution and child_process for local execution, meaning that both local command injection and remote command execution attacks are possible depending on how the package is configured and used.
This vulnerability creates a severe operational impact by enabling complete system compromise when applications using backmeup pass user-controllable inputs to the affected parameters. An attacker can execute arbitrary commands with the privileges of the process running backmeup, potentially leading to full system compromise, data exfiltration, privilege escalation, or persistence mechanisms being established. The attack surface is broad since any application that accepts user input for backup operations and passes it through backmeup's option values becomes vulnerable. This represents a critical security flaw that aligns with CWE-78 (Improper Neutralization of Special Elements used in an OS Command) and follows patterns commonly seen in command injection attacks documented in the MITRE ATT&CK framework under T1059.001 (Command and Scripting Interpreter: PowerShell) and related execution techniques.
The primary mitigation strategy involves implementing proper argument array usage instead of string concatenation for shell commands, utilizing execFile or spawn functions rather than exec or shell execution methods. Applications should avoid direct string concatenation of user inputs into shell command strings and instead implement robust input validation, sanitization, and escaping mechanisms specific to shell contexts. Additionally, the package itself requires immediate remediation by either properly escaping special characters in user inputs or by restructuring command execution to use argument arrays rather than shell string construction. Organizations should also consider implementing principle of least privilege for processes using backmeup, limiting the execution privileges available to prevent escalation of compromised systems. Regular security auditing and input validation practices should be enforced throughout application codebases to prevent similar vulnerabilities from manifesting in other components.