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Vulnerability record · CVE-2021-43797 · published 9 December 2021

CVE-2021-43797: Netty http request smuggling vulnerability

Netty · Netty

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

6.5 CVSS 3.1 Medium EPSS 2.7% · top 14.7% CWE-444 · HTTP request smuggling
6.5CVSS 3.1 base score, v2 4.3
2.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
18Affected product versions listed by NVD
14References
17 Jun 2026Last modified by NVD

Description

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. Netty prior to version 4.1.71.Final skips control chars when they are present at the beginning / end of the header name. It should instead fail fast as these are not allowed by the spec and could lead to HTTP request smuggling. Failing to do the validation might cause netty to "sanitize" header names before it forward these to another remote system when used as proxy. This remote system can't see the invalid usage anymore, and therefore does not do the validation itself. Users should upgrade to version 4.1.71.Final.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Affected products

18 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/netty/netty/commit/07aa6b5938a8b6ed7a6586e066400e2643897323 PatchThird Party Advisory
https://github.com/netty/netty/security/advisories/GHSA-wx5j-54mm-rqqq Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/01/msg00008.html Mailing ListThird Party Advisory
https://security.netapp.com/advisory/ntap-20220107-0003/ Third Party Advisory
https://www.debian.org/security/2023/dsa-5316 Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory
https://github.com/netty/netty/commit/07aa6b5938a8b6ed7a6586e066400e2643897323 PatchThird Party Advisory
https://github.com/netty/netty/security/advisories/GHSA-wx5j-54mm-rqqq Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/01/msg00008.html Mailing ListThird Party Advisory
https://security.netapp.com/advisory/ntap-20220107-0003/ Third Party Advisory
https://www.debian.org/security/2023/dsa-5316 Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-43797), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.