CVE-2025-12642: Lighttpd

Critical severity, CVSS 9.1. EPSS: 0.4% chance of exploitation in the next 30 days.

lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks. Successful exploitation may allow an attacker to: * Bypass access control rules * Inject unsafe input into backend logic that trusts request headers * Execute HTTP Request Smuggling attacks under some conditions This issue affects lighttpd1.4.80

Affected products

• Lighttpd Lighttpd: version 1.4.80 only

Published 2025-11-03. Last modified 2026-06-17.