CVE-2021-43797

HTTP fails to validate against control chars in header names which may lead to HTTP request smuggling

MEDIUM
6.5
CVSS Score
Published: December 9, 2021 at 12:00 AM UTC
Updated: October 8, 2026 at 10:17 PM UTC
18 products affected across 5 vendorsDebian LinuxOnCommand Workflow AutomationSnapCenter

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Severity
MEDIUM6.5
Exploit prediction
EPSS 3%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-444

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