CVE-2026-86427 in LibreNMS
Summary
by MITRE • 09/07/2026
LibreNMS before 26.8.0 contains an argument injection vulnerability in the graph_title parameter that allows authenticated attackers to inject arbitrary rrdtool arguments by breaking out of double-quote escaping. Attackers can inject DEF and LINE arguments to read RRD files from unauthorized devices, or use newline injection to execute arbitrary rrdtool commands, bypassing per-device authorization checks.
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability identified in LibreNMS versions prior to 26.8.0 represents a critical security flaw rooted in improper input validation and sanitization within the graph_title parameter processing logic. This argument injection vulnerability allows authenticated attackers to manipulate how rrdtool, the Round Robin Database tool used for network monitoring data visualization, constructs its command line arguments. The core technical failure lies in the application's handling of user-supplied input where double-quote escaping mechanisms are insufficient or incorrectly implemented. By carefully crafting specific payloads that break out of these quoted strings, an attacker can inject arbitrary rrdtool arguments directly into the execution context. This flaw effectively bypasses the intended boundary between user-provided metadata and system-level command construction, creating a pathway for unauthorized code execution within the scope of the application's process privileges.
From a technical perspective, this vulnerability manifests in two distinct but related attack vectors that exploit different aspects of rrdtool functionality. The first vector involves injecting DEF arguments to read data from Round Robin Database files associated with devices or interfaces that the attacker does not have explicit authorization to access. Since LibreNMS aggregates monitoring data for numerous network elements, unauthorized access to these RRD files can reveal sensitive performance metrics, topology details, and potentially other proprietary operational intelligence about the monitored infrastructure. The second vector is more severe, involving newline injection techniques. By inserting newlines into the graph_title parameter, an attacker can terminate the current command line argument and append additional rrdtool commands. This allows for the execution of arbitrary system-level operations through the rrdtool binary, effectively achieving remote code execution or significant data exfiltration capabilities depending on how the injected arguments are structured and what permissions the web server process holds.
The operational impact of this vulnerability is substantial due to its potential for both information disclosure and privilege escalation within the application's context. For organizations relying on LibreNMS for critical network visibility, an exploited instance could lead to a comprehensive compromise of monitored assets' data integrity and confidentiality. Attackers can map out internal network structures by accessing RRD files from unauthorized devices, which aids in further reconnaissance efforts against the target environment. Furthermore, if the newline injection vector is successfully leveraged to execute arbitrary commands, it may allow attackers to pivot into other parts of the infrastructure, install backdoors, or disrupt monitoring services entirely. The fact that this requires authentication does not mitigate the risk significantly, as compromised credentials are common in modern threat landscapes, and internal threats from malicious insiders can also exploit this flaw without needing external access vectors.
This vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection, specifically within a context where input is not properly validated before being passed to system utilities. Additionally, the ability to read unauthorized resources corresponds closely to CWE-200 Exposure of Sensitive Information to an Unauthorized Actor and CWE-862 Missing Authorization for critical functions involving data access from restricted devices. In terms of tactical classification under MITRE ATT&CK frameworks, this behavior maps to T1059 Command and Scripting Interpreter where the attacker utilizes rrdtool as a vehicle for execution, and potentially T1005 Data from Local System if focusing on the exfiltration aspect via DEF argument injection. The exploitation technique also reflects aspects of T1190 Exploit Public-Facing Application if the authentication boundary is bypassed through other means or if weak credentials are targeted.
Mitigation strategies must prioritize immediate patching to version 26.8.0 or later, where these input validation and escaping mechanisms have been corrected by the LibreNMS development team. In environments where upgrading is not immediately feasible, network-level controls should be implemented to restrict outbound connections from the web server process that could facilitate command execution callbacks if such a vector exists in modified versions. Input filtering rules at the WAF or reverse proxy layer can also provide temporary relief by blocking requests containing suspicious patterns associated with rrdtool argument injection, such as specific DEF prefixes or newline characters within graph_title parameters. However, these compensating controls are not substitutes for applying the official patch, which addresses the root cause in the application code itself. Regular audits of authentication logs and monitoring for unusual spikes in RRD file access from unexpected sources can also aid in early detection of exploitation attempts against unpatched instances.