CVE-2026-26991 LibreNMS vulnerable to Stored Cross-site Scripting through unsanitized /device-groups name
Attackers with admin privileges can inject malicious scripts via unsanitized device group names, leading to stored XSS attacks in LibreNMS.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-26991?
CVE-2026-26991 is a medium-severity cross-site scripting vulnerability in Librenms Librenms, published on 20 Feb 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
LibreNMS is an auto-discovering PHP/MySQL/SNMP based network monitoring tool. In versions 26.1.1 and below, the device group name is not sanitized, allowing attackers with admin privileges to perform Stored Cross-Site Scripting (XSS) attacks. When a user adds a device group, an HTTP POST request is sent to the Request-URI "/device-groups". The name of the newly created device group is stored in the value of the name parameter. After the device group is created, the entry is displayed along with relevant buttons such as Rediscover Devices, Edit, and Delete. This issue has been fixed in version 26.2.0.
Weakness: CWE-79
Which versions are affected by CVE-2026-26991?
2 open source packages ship an affected version, including librenms/librenms. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
librenms/librenms Packagist | All versions | 26.2.0 |
librenms/librenms Packagist | All versions | 26.2.0 |
Products include Librenms Librenms.
How do I fix CVE-2026-26991?
Upgrade librenms/librenms to 26.2.0 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-26991 being exploited?
There is no known exploitation of CVE-2026-26991 in the wild and no public exploit code.
Other vulnerabilities in Librenms Librenms
Sources
Also known as GHSA-5pqf-54qp-32wx.