What is CVE-2026-42581?

CVE-2026-42581 is a medium-severity vulnerability in Netty, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 5.8/10. Published 2026-05-13.

How severe is CVE-2026-42581?

Medium severity. CVSS v3 base score is 5.8 out of 10.

Vulnerability in Netty

CVE-2026-42581

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-…

Vulnerability class: HTTP Request Smuggling

EPSS: 0.000 (4.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N.

Affected products

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, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42581?: CVE-2026-42581 is a medium-severity vulnerability in Netty, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 5.8/10. Published 2026-05-13.
How severe is CVE-2026-42581?: Medium severity. CVSS v3 base score is 5.8 out of 10.