How to fix CVE-2019-25375?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Is Opnsense affected by CVE-2019-25375?

Organizations using OPNsense 19.1 should be aware of moderate risk from CVE-2019-25375, a cross-site scripting vulnerability rated CVSS 6.1. Attackers could inject scripts to steal sessions or perform actions as authenticated users. Proof-of-concept code is publicly available.

CVE-2019-25375

MEDIUM

2026-02-15 [email protected]

6.1

CVSS 3.1

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

PoC Detected

Feb 18, 2026 - 19:11 vuln.today

Public exploit code

CVE Published

Feb 15, 2026 - 14:16 nvd

MEDIUM 6.1

Description

OPNsense 19.1 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to inject malicious scripts by submitting crafted input to the mailserver parameter. Attackers can send POST requests to the monit interface with JavaScript payloads in the mailserver parameter to execute arbitrary code in users' browsers.

Analysis

Technical Context

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects the mailserver component of Opnsense. OPNsense 19.1 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to inject malicious scripts by submitting crafted input to the mailserver parameter. Attackers can send POST requests to the monit interface with JavaScript payloads in the mailserver parameter to execute arbitrary code in users' browsers.

Affected Products

Vendor: Opnsense. Product: Opnsense. Versions: up to 19.1. Component: mailserver.

Remediation

Monitor vendor advisories for a patch. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +0.0

CVSS: +30

POC: +20

CVE-2019-25375 vulnerability details – vuln.today

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CVE-2019-25375

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CVE-2019-25375

CVSS Vector

Lifecycle Timeline

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Description

Analysis

Technical Context

Affected Products

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External POC / Exploit Code