CVE-2019-25378 Smoothwall Express 3.1 'proxy.cgi' Cross-Site Scripting

Medium 5.1 Published 16 Feb 2026 Updated 5 Mar 2026

Attackers can inject malicious scripts into the proxy configuration page, allowing arbitrary JavaScript execution in users' browsers.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2019-25378?

CVE-2019-25378 is a medium-severity cross-site scripting vulnerability in Smoothwall Express, published on 16 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Smoothwall Express 3.1-SP4-polar-x86_64-update9 contains multiple cross-site scripting vulnerabilities in the proxy.cgi endpoint that allow attackers to inject malicious scripts through parameters including CACHE_SIZE, MAX_SIZE, MIN_SIZE, MAX_OUTGOING_SIZE, and MAX_INCOMING_SIZE. Attackers can submit POST requests with script payloads to store or reflect arbitrary JavaScript code that executes in users' browsers when the proxy configuration page is accessed.

Weakness: CWE-79

Which versions are affected by CVE-2019-25378?

It affects 1 product.

Products include Smoothwall Smoothwall Express.

How do I fix CVE-2019-25378?

No fix has been published for CVE-2019-25378 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2019-25378 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2019-25378 exists.

Sources

Also known as GHSA-hcvh-8pvq-9ppx.