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CVE-2025-12642

9.1 · CRITICAL

lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing.

Published Nov 3, 2025CWE-444EPSS 0.37%

Overview

CVE-2025-12642 is a critical-severity vulnerability. It was published on November 3, 2025 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

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

How CyberStrike helps

Frequently asked questions

What is CVE-2025-12642?

CVE-2025-12642 is a critical-severity vulnerability. It was published on November 3, 2025 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2025-12642?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2025-12642?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-12642?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-12642 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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