CVE-2026-27016Public exploitNetwork attack vector

Stored XSS via unescaped Custom OID unit

Published Feb 20, 2026 · Updated Feb 20, 2026

Stored XSS in LibreNMS 24.10.0 through 26.1.1 allows remote authenticated users to execute JavaScript via a Custom OID unit value. includes/html/forms/customoid.inc.php stores the unit POST value without strip_tags(), and graphs/customoid.inc.php later emits it without HTML escaping. A user with device edit permissions can plant the value, and execution requires another user to view the affected device graph, exposing that viewer's session data and browser-authorized actions.

CVSS severity5.4
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in LibreNMS 24.10.0 through 26.1.1 allows remote authenticated users to execute JavaScript via a Custom OID unit value. includes/html/forms/customoid.inc.php stores the unit POST value without strip_tags(), and graphs/customoid.inc.php later emits it without HTML escaping. A user with device edit permissions can plant the value, and execution requires another user to view the affected device graph, exposing that viewer's session data and browser-authorized actions.

The record

CVE
CVE-2026-27016
Published
Feb 20, 2026
Updated
Feb 20, 2026
Vendor
LibreNMS
Product
LibreNMS
Classifications
CWE-79, CWE-116, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 24.10.0, < 26.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

LibreNMS · LibreNMSversion=>= 24.10.0, < 26.2.0

Published CVSS scores

5.4GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-116Improper Encoding or Escaping of Output
T1059.007JavaScript/JScript

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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