Vulnerability in Lighttpd
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
Vulnerability class: HTTP Request Smuggling
EPSS: 0.003 (26.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
Affected products
- Lighttpd — versions 1.4.80
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2025-12642?
- CVE-2025-12642 is a critical-severity vulnerability in Lighttpd, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 9.1/10. Published 2025-11-03.
- How severe is CVE-2025-12642?
- Critical severity. CVSS v3 base score is 9.1 out of 10.