CVE-2021-43797mediumCWE-444

CVE-2021-43797: medium-severity vulnerability in netty

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

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.5epss 2.9%
In short

Netty fails to properly validate HTTP header names that contain control characters at the beginning or end, which could allow attackers to manipulate requests when the framework is used as a proxy, potentially leading to HTTP request smuggling attacks.

Technical detail

Netty prior to 4.1.71.Final strips control characters from header names instead of rejecting them outright, violating HTTP specifications. When used as a proxy, this sanitization allows crafted headers to bypass validation in backend systems, enabling HTTP request smuggling attacks where attackers inject malicious requests through specially crafted header names.

Summary generated and translated by AI from the official 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
netty · netty
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