by Kastro
Paper/Archive/CVE-2025-12642

CVE-2025-12642

lighttpd lighttpd — HTTP Header Smuggling via Trailer Merge

EPSS 0.4%CVSS 9.1
critical.is priorityof 100
33
CVSS 9.1 (NVD)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 30.6.306 × 206.1No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
lighttpd1.4.80 – < 1.4.811.4.81CNA

Scores by source

NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Toreon (CNA)6.9CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: partial

References

refgithub.com/lighttpd/lighttpd1.4/commit/35cb89c103877de62d6b63d0804255475d77e5e1