{"id":"CVE-2025-12642","aliases":["EUVD-2025-37517","GHSA-fvx8-q97q-cw73","UBUNTU-CVE-2025-12642"],"status":"published","title":"HTTP Header Smuggling via Trailer Merge","description":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks.\n\nSuccessful exploitation may allow an attacker to:\n\n  *  Bypass access control rules\n  *  Inject unsafe input into backend logic that trusts request headers\n  *  Execute HTTP Request Smuggling attacks under some conditions\n\n\nThis issue affects lighttpd1.4.80","severity":{"version":"4.0","score":6.9,"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00368,"percentile":0.30951,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-444"],"published":"2025-11-03T19:36:17Z","modified":"2026-10-24T07:22:15Z","affected":[{"source":"osv","ecosystem":"Ubuntu:Pro:14.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.31-3ubuntu3","1.4.33-1ubuntu1","1.4.33-1+nmu2ubuntu1","1.4.33-1+nmu2ubuntu2","1.4.33-1+nmu2ubuntu2.1","1.4.33-1+nmu2ubuntu2.1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.35-4ubuntu1","1.4.35-4ubuntu2","1.4.35-4ubuntu2.1","1.4.35-4ubuntu2.1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.45-1ubuntu1","1.4.45-1ubuntu3","1.4.45-1ubuntu3+esm1","1.4.45-1ubuntu3.18.04","1.4.45-1ubuntu3.18.04+esm1","1.4.45-1ubuntu3.18.04.1","1.4.45-1ubuntu3.18.04.1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.53-4ubuntu2","1.4.54-2ubuntu1","1.4.55-1ubuntu1","1.4.55-1ubuntu1.20.04.1","1.4.55-1ubuntu1.20.04.2"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.59-1ubuntu2","1.4.59-1ubuntu3","1.4.63-1ubuntu1","1.4.63-1ubuntu2","1.4.63-1ubuntu3","1.4.63-1ubuntu3.1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.69-1ubuntu1","1.4.69-1ubuntu2","1.4.73-1ubuntu1","1.4.73-1ubuntu2","1.4.74-1ubuntu2","1.4.74-1ubuntu3"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.79-1ubuntu1","1.4.79-2ubuntu1","1.4.82-2ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.82-2ubuntu2","1.4.84-1ubuntu3","1.4.85-1ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"lighttpd","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.4.82-2ubuntu1","1.4.82-2ubuntu2"]}],"products":[{"vendor":"lighttpd","product":"lighttpd"}],"references":[{"url":"https://github.com/lighttpd/lighttpd1.4/commit/35cb89c103877de62d6b63d0804255475d77e5e1","tags":["Patch","fix","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-12642"},{"url":"https://github.com/advisories/GHSA-fvx8-q97q-cw73"},{"url":"https://ubuntu.com/security/CVE-2025-12642","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2025-12642","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2025-12642","title":"HTTP Header Smuggling via Trailer Merge","description":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks.\n\nSuccessful exploitation may allow an attacker to:\n\n  *  Bypass access control rules\n  *  Inject unsafe input into backend logic that trusts request headers\n  *  Execute HTTP Request Smuggling attacks under some conditions\n\n\nThis issue affects lighttpd1.4.80","status":"published","published":"2025-11-03T19:36:17.011Z","modified":"2025-11-03T19:44:09.174Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium","assessor":"cna"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:32:41.743125Z"}],"euvd":[{"id":"EUVD-2025-37517","description":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks.\n\nSuccessful exploitation may allow an attacker to:\n\n  *  Bypass access control rules\n  *  Inject unsafe input into backend logic that trusts request headers\n  *  Execute HTTP Request Smuggling attacks under some conditions\n\n\nThis issue affects lighttpd1.4.80","status":"published","published":"2025-11-03T19:36:17Z","modified":"2025-11-03T19:44:09Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium"}],"updated_at":"2026-11-02T19:49:33.639996Z"}],"ghsa":[{"id":"GHSA-fvx8-q97q-cw73","title":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This...","description":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks.\n\nSuccessful exploitation may allow an attacker to:\n\n  *  Bypass access control rules\n  *  Inject unsafe input into backend logic that trusts request headers\n  *  Execute HTTP Request Smuggling attacks under some conditions\n\n\nThis issue affects lighttpd1.4.80","status":"published","published":"2025-11-03T21:34:45Z","modified":"2025-11-12T15:31:28Z","cvss":[{"version":"4.0","score":6.9,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:04:45.782037Z"}],"nvd":[{"id":"CVE-2025-12642","description":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks.\n\nSuccessful exploitation may allow an attacker to:\n\n  *  Bypass access control rules\n  *  Inject unsafe input into backend logic that trusts request headers\n  *  Execute HTTP Request Smuggling attacks under some conditions\n\n\nThis issue affects lighttpd1.4.80","status":"published","published":"2025-11-03T20:17:06.41Z","modified":"2026-10-19T13:10:00.11Z","cvss":[{"version":"4.0","score":6.9,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"primary"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:11:41.607433Z"}],"osv":[{"id":"CVE-2025-12642","description":"lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks.\n\nSuccessful exploitation may allow an attacker to:\n\n  *  Bypass access control rules\n  *  Inject unsafe input into backend logic that trusts request headers\n  *  Execute HTTP Request Smuggling attacks under some conditions\n\n\nThis issue affects lighttpd1.4.80","status":"published","published":"2025-11-03T20:17:06.41Z","modified":"2026-10-24T07:22:15.959447441Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"updated_at":"2026-11-02T15:44:46.024537Z"},{"id":"UBUNTU-CVE-2025-12642","description":"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","status":"published","published":"2025-11-03T20:17:00Z","modified":"2026-10-17T12:57:00.63158654Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"updated_at":"2026-11-02T16:55:20.144818Z"}]}}