CVE-2019-25375Public exploitNetwork attack vector

Browser script execution via unescaped mailserver parameter

Published Feb 15, 2026 · Updated Feb 15, 2026

Reflected XSS in the OPNsense 19.1 monit interface allows remote attackers to execute scripts in a user's browser via a crafted POST request. The /ui/monit handler reflects the mailserver parameter into an HTML response without context-appropriate escaping, causing injected event-handler markup to run as script. Exploitation requires a user to render the crafted response; the script then runs in that user's OPNsense web-interface origin and can read or modify session-accessible data.

CVSS severity5.1
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in the OPNsense 19.1 monit interface allows remote attackers to execute scripts in a user's browser via a crafted POST request. The /ui/monit handler reflects the mailserver parameter into an HTML response without context-appropriate escaping, causing injected event-handler markup to run as script. Exploitation requires a user to render the crafted response; the script then runs in that user's OPNsense web-interface origin and can read or modify session-accessible data.

The record

CVE
CVE-2019-25375
Published
Feb 15, 2026
Updated
Feb 15, 2026
Vendor
Deciso B.V.
Product
OPNsense
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 15, 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=19.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Deciso B.V. · OPNsenseversion=19.1

Published CVSS scores

6.1VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/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')
T1059.007Command and Scripting Interpreter: JavaScript/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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