CVE-2014-8990 in Lsyncd
Summary
by MITRE
default-rsyncssh.lua in Lsyncd 2.1.5 and earlier allows remote attackers to execute arbitrary commands via shell metacharacters in a filename.
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Analysis
by VulDB Data Team • 12/08/2024
The vulnerability identified as CVE-2014-8990 resides within the default-rsyncssh.lua script component of Lsyncd version 2.1.5 and earlier. This issue represents a critical command injection flaw that arises from inadequate input sanitization when processing filenames during synchronization operations. Lsyncd functions as a lightweight daemon that synchronizes local directories with remote servers using rsync over SSH connections, making it a crucial component in many file synchronization workflows across enterprise environments.
The technical flaw manifests when the default-rsyncssh.lua script fails to properly escape or sanitize shell metacharacters present in filenames being processed. When a malicious user uploads or modifies a file with special shell characters such as semicolons, ampersands, backticks, or pipes within the filename, these characters can be interpreted by the underlying shell during command execution. This occurs because the script directly incorporates user-supplied filenames into shell command constructions without proper sanitization or escaping mechanisms, creating an environment where arbitrary command execution becomes possible through crafted filenames.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables remote attackers to execute arbitrary commands with the privileges of the user running the Lsyncd daemon. In typical deployment scenarios, this daemon often runs with elevated privileges to perform synchronization tasks, potentially allowing attackers to gain unauthorized access to sensitive system resources. The vulnerability affects environments where Lsyncd is configured to synchronize directories containing user-uploaded content or where untrusted data sources feed into the synchronization process. This creates a significant risk for organizations relying on Lsyncd for automated backup, content distribution, or file sharing operations.
Security practitioners should recognize this vulnerability as a classic command injection flaw that aligns with CWE-77 and CWE-88 categories, representing improper neutralization of special elements used in command execution. The attack vector follows patterns consistent with ATT&CK technique T1059.001 for command and script injection, where adversaries leverage application flaws to execute malicious commands. Organizations should immediately upgrade to Lsyncd version 2.1.6 or later, which includes proper input sanitization for filename handling. Additionally, implementing network segmentation, restricting Lsyncd access to trusted networks, and monitoring for unusual file synchronization patterns can provide additional layers of defense. The vulnerability demonstrates the critical importance of proper input validation and escaping mechanisms in scripts that interface with shell commands, particularly in automated system administration tools where the consequences of command injection can be severe.