CVE-2025-12642 MEDIUM

CVE-2025-12642: HTTP Header Smuggling via Trailer Merge

Vendor Lighttpd
Product lighttpd
Weakness CWE-444
Published November 3, 2025
Last update November 3, 2025

CVSS base score

6.9/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

What the vulnerability does

01Description

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

Key dates

02Disclosure timeline

November 3, 2025 CVE published
November 3, 2025 Record updated