CVE-2025-12642

HTTP Header Smuggling via Trailer Merge

Published Nov 3, 2025 CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed
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

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
CPEs cpe:2.3:a:lighttpd:lighttpd:1.4.80:*:*:*:*:*:*:*
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

Type Values Removed Values Added
First Time appeared Lighttpd
Lighttpd lighttpd
Vendors & Products Lighttpd
Lighttpd lighttpd
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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
Title HTTP Header Smuggling via Trailer Merge
Weaknesses CWE-444
References
Metrics cvssV4_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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Toreon
Published
Updated
Nov 3, 2025, 7:44 PM
Reserved
Nov 3, 2025, 7:34 PM
Status
Analyzed
Published
Nov 3, 2025, 8:17 PM
Modified
Oct 19, 2026, 1:10 PM