What is CVE-2026-42585?

CVE-2026-42585 is a medium-severity vulnerability in Io.netty Netty-codec-http, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 6.5/10. Published 2026-05-13.

How severe is CVE-2026-42585?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Io.netty Netty-codec-http

CVE-2026-42585

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks. This vulnerability is fixed in 4.2.13…

Vulnerability class: HTTP Request Smuggling

EPSS: 0.000 (1.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

Affected products

Io.netty Netty-codec-http — versions >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Final
Netty — versions >= 4.2.0.Alpha1, < 4.2.13.Final, < 4.1.133.Final

Weakness classification (CWE)

CWE-444 — Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling)

References

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

Frequently asked questions

What is CVE-2026-42585?: CVE-2026-42585 is a medium-severity vulnerability in Io.netty Netty-codec-http, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 6.5/10. Published 2026-05-13.
How severe is CVE-2026-42585?: Medium severity. CVSS v3 base score is 6.5 out of 10.