CVE-2026-26987

LibreNMS affected by reflected XSS via email field

5.3 MediumFix available

LibreNMS is an auto-discovering PHP/MySQL/SNMP based network monitoring tool. Versions 25.12.0 and below are vulnerable to Reflected XSS attacks via email field. This issue has been fixed in version 26.2.0.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Passive

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: None

Exploit likelihood

0.34%Up 0.3 points since Feb 20, 2026

What each source reports

CVE List Score used 5.3

LibreNMS affected by reflected XSS via email field

Record: CVE-2026-26987
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness: CWE-79
Updated: 2026-11-02

EUVDEUVD-2026-8401 5.3

Record: EUVD-2026-8401
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-gqx7-99jw-6fpr 5.3

LibreNMS affected by reflected xss via email field

Summary

reflected xss via email field

Details

visit http://127.0.0.1/settings/alerting/email
in the email address input but this payload <img src=1 onerror=alert(document.cookie)>
notice the alert

PoC

video attached with the report https://github.com/user-attachments/assets/c1b443f5-85c6-4545-b04f-def06d82b42e

Impact

can lead to ATO

Record: GHSA-gqx7-99jw-6fpr
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness: CWE-79
Updated: 2026-11-02

NVD 5.3

Record: CVE-2026-26987
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSV 5.3

LibreNMS affected by reflected XSS via email field

Record: CVE-2026-26987
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness: CWE-79
Updated: 2026-11-02

OSVGHSA-gqx7-99jw-6fpr 5.3

LibreNMS affected by reflected xss via email field

Summary

reflected xss via email field

Details

visit http://127.0.0.1/settings/alerting/email
in the email address input but this payload <img src=1 onerror=alert(document.cookie)>
notice the alert

PoC

video attached with the report https://github.com/user-attachments/assets/c1b443f5-85c6-4545-b04f-def06d82b42e

Impact

can lead to ATO

Record: GHSA-gqx7-99jw-6fpr
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness: CWE-79
Updated: 2026-11-02

Affected products

librenms

Affected packages

Affected packages
Package	Affected	Fixed
`librenms/librenms` Packagist	before 26.2.0	26.2.0
`librenms/librenms` Packagist	before 26.2.0, plus listed versions 1.191.201.20.11.211.22 Show 45 moreShow less 1.22.011.231.241.251.261.271.281.291.301.30.011.311.31.011.31.021.31.031.321.32.011.331.33.011.341.351.361.36.011.371.381.391.401.411.421.42.011.431.441.451.461.471.481.48.11.491.501.50.11.511.521.531.53.11.541.55	26.2.0

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-26987 is a medium vulnerability (CVSS 5.3) in Librenms, published February 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. Fixed in librenms/librenms 26.2.0.

References

This page doesn't list everything

Left out here: 99 versions. The JSON record has them.