CVE-2026-26987: Librenms/librenms Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-gqx7-99jw-6fpr
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CWE-79
Published
Advisory Summary

CVE-2026-26987 is a MODERATE cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Librenms/librenms libraries in the Packagist ecosystem. The issue involves librenms affected by reflected xss via email field. Remediation is available by upgrading affected packages to version 26.2.0.

CVE-2026-26987 at a Glance

CVE Identifier CVE-2026-26987
GHSA Identifier GHSA-gqx7-99jw-6fpr
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Librenms/librenms
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-26987

To remediate this vulnerability, upgrade all affected Librenms/librenms dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

librenms/librenms fixed: 26.2.0 
Upgrade librenms/librenms to 26.2.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for librenms/librenms

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-26987, inspect your project dependencies for Librenms/librenms:

inspect dependencies for librenms/librenms

Analyze the terminal output to locate any version of Librenms/librenms in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.2.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Librenms/librenms, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary reflected xss via email field ### Details 1. visit `http://127.0.0.1/settings/alerting/email` 2. in the email address input but this payload `<img src=1 onerror=alert(document.cookie)>` 3. 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

CVE-2026-26987 Affected Librenms/librenms Versions

1 component(s)
Fixed Versions:
26.2.0
Product / Package Ecosystem Affected Versions Fixed Version
librenms/librenms
 Packagist
< 26.2.0
26.2.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/librenms/librenms/security/advisories/GHSA-gqx7-99jw-6fpr
NVD — CVE-2026-26987 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-26987
Librenms/librenms Source Repository REPOSITORY
https://github.com/librenms/librenms/pull/19038
Security Fix Commit FIX COMMIT
https://github.com/librenms/librenms/commit/8e626b38ef92e240532cdac2ac7e38706a71208b
Librenms/librenms Source Repository REPOSITORY
https://github.com/librenms/librenms
Librenms/librenms Release RELEASE
https://github.com/librenms/librenms/releases/tag/26.2.0

Frequently Asked Questions

What is CVE-2026-26987?
CVE-2026-26987 is a security vulnerability in Librenms/librenms involving LibreNMS affected by reflected xss via email field under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Librenms/librenms versions are affected?
Affected versions include releases prior to 26.2.0 across affected packages: librenms/librenms.
What version fixes CVE-2026-26987?
Upgrading to 26.2.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is librenms/librenms affected?
Yes, librenms/librenms is affected in releases prior to 26.2.0. Upgrade your dependency to 26.2.0 or later.
What CWE is associated with CVE-2026-26987?
CVE-2026-26987 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check Packagist dependencies for CVE-2026-26987?
Run the dependency tree command: 'inspect dependencies for librenms/librenms'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gqx7-99jw-6fpr",
  "modified" : "2026-02-20T16:48:17Z",
  "published" : "2026-02-18T22:07:06Z",
  "aliases" : [ "CVE-2026-26987" ],
  "summary" : "LibreNMS affected by reflected xss via email field ",
  "details" : "### Summary\nreflected xss via email field \n\n### Details\n 1. visit `http://127.0.0.1/settings/alerting/email`\n 2. in the email address input but this payload \n `<img src=1 onerror=alert(document.cookie)>` \n3. notice the alert \n### PoC\n- video attached with the report\nhttps://github.com/user-attachments/assets/c1b443f5-85c6-4545-b04f-def06d82b42e\n\n\n### Impact\ncan lead to ATO",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "librenms/librenms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.2.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/librenms/librenms/security/advisories/GHSA-gqx7-99jw-6fpr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-26987"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/librenms/librenms/pull/19038"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/librenms/librenms/commit/8e626b38ef92e240532cdac2ac7e38706a71208b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/librenms/librenms"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/librenms/librenms/releases/tag/26.2.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-18T22:07:06Z",
    "nvd_published_at" : "2026-02-20T02:16:54Z"
  }
}