CVE-2026-84191Public exploitNetwork attack vectorHinoki check available

Stored XSS via unescaped SNMP VRF fields

Published Sep 1, 2026 · Updated Sep 1, 2026

Stored XSS in LibreNMS before 26.5.0 allows remote attackers controlling a monitored device to execute JavaScript through SNMP data. VRF discovery stores mplsVpnVrfDescription, vrf_name, and route-distinguisher values, and the VRF PHP views echo them into HTML and an event attribute without escaping. Exploitation requires control of a monitored device or interception of insecure SNMP traffic plus a user viewing a VRF page, enabling browser-session data theft or actions with that user's privileges.

CVSS severity5.3
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Stored XSS in LibreNMS before 26.5.0 allows remote attackers controlling a monitored device to execute JavaScript through SNMP data. VRF discovery stores mplsVpnVrfDescription, vrf_name, and route-distinguisher values, and the VRF PHP views echo them into HTML and an event attribute without escaping. Exploitation requires control of a monitored device or interception of insecure SNMP traffic plus a user viewing a VRF page, enabling browser-session data theft or actions with that user's privileges.

The record

CVE
CVE-2026-84191
Published
Sep 1, 2026
Updated
Sep 1, 2026
Vendor
LibreNMS
Product
LibreNMS
Classifications
CWE-79, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

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

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=0 <26.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LibreNMS · LibreNMSversion=0 <26.5.0

Published CVSS scores

6.1LibreNMSCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.3VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA: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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1539Steal Web Session Cookie

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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