What is CVE-2026-42578?

CVE-2026-42578 is a high-severity vulnerability in Netty, classified under HTTP Response Splitting. CVSS score: 7.5/10. Published 2026-05-13.

How severe is CVE-2026-42578?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Netty

CVE-2026-42578

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty's HttpProxyHandler constructs HTTP CONNECT requests with header validation explicitly disabled. The newInitialMessage() me…

EPSS: 0.000 (1.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

Affected products

Netty — versions >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Final

Weakness classification (CWE)

CWE-113 — HTTP Response Splitting

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42578?: CVE-2026-42578 is a high-severity vulnerability in Netty, classified under HTTP Response Splitting. CVSS score: 7.5/10. Published 2026-05-13.
How severe is CVE-2026-42578?: High severity. CVSS v3 base score is 7.5 out of 10.