CVE-2026-26352: Smoothwall Express < 3.1 Update 13 Stored XSS in vpnmain.cgi via VPN_IP Parameter

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-30 · updated 2026-06-17
Weakness: CWE-79

Description

Smoothwall Express versions prior to 3.1 Update 13 contain a stored cross-site scripting vulnerability in the /cgi-bin/vpnmain.cgi script due to improper sanitation of the VPN_IP parameter. Authenticated attackers can inject arbitrary JavaScript through VPN configuration settings that executes when the affected page is viewed by other users.

Affected products

Smoothwall Express: through 3.0; 3.1-update1, 3.1-update10, 3.1-update11, 3.1-update12, 3.1-update2, 3.1-update3 (+6)

References

https://community.smoothwall.org/forum/viewtopic.php?t=45095
https://www.vulncheck.com/advisories/smoothwall-express-stored-xss-in-vpnmain-cgi-via-vpn-ip-parameter

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