Headline
GHSA-gcgp-q2jq-fw52: LibreNMS has Stored Cross-site Scripting vulnerability in "Alert Templates" feature
Summary
A Self Cross-Site Scripting (Self-XSS) vulnerability in the “Alert Templates” feature allows users to inject arbitrary JavaScript into the alert template’s name. This script executes immediately upon submission but does not persist after a page refresh.
Details
The vulnerability occurs when creating an alert template in the LibreNMS interface. Although the application sanitizes the “name” field when storing it in the database, this newly created template is immediately added to the table without any sanitization being applied to the name, allowing users to inject arbitrary JavaScript. This script executes when the template is created but does not persist in the database, thus preventing stored XSS.
For instance, the following payload can be used to exploit the vulnerability:
test1<script>{onerror=alert}throw 1337</script>
The root cause of this vulnerability lies in the lack of sanitization of the “name” variable before it is rendered in the table. The vulnerability exists because the bootgrid function of the jQuery grid plugin does not sanitize the text being added to the table. Although tags are stripped before being added to the database (as shown in the code below), the vulnerability still allows Self-XSS during the creation of the template.
Where the variable is being sanitized before being stored in the database: https://github.com/librenms/librenms/blob/0e741e365aa974a74aee6b43d1b4b759158a5c7e/includes/html/forms/alert-templates.inc.php#L40
Where the vulnerability is happening: https://github.com/librenms/librenms/blob/0e741e365aa974a74aee6b43d1b4b759158a5c7e/includes/html/modal/alert_template.inc.php#L205
PoC
- Navigate to the “Alert Templates” creation page in the LibreNMS interface.
- In the “Name” field, input the following payload:
test1<script>{onerror=alert}throw 1337</script> - Submit the form to create the alert template.
- Observe that the JavaScript executes immediately, triggering an alert popup. However, this code does not persist after refreshing the page.
Impact
This is a Self Cross-Site Scripting (Self-XSS) vulnerability. Although the risk is lower compared to traditional XSS, it can still be exploited through social engineering or tricking users into entering or interacting with malicious code. This can lead to unauthorized actions or data exposure in the context of the affected user’s session.
Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.