CVE-2025-12642

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