CVE-2021-21295 Vulnerability Details

  /     /     /  

CVE-2021-21295 Metadata Quick Info

CVE Published: 09/03/2021 | CVE Updated: 03/08/2024 | CVE Year: 2021
Source: GitHub_M | Vendor: netty | Product: io.netty:netty-codec-http2
Status : PUBLISHED

CVE-2021-21295 Description

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty (io.netty:netty-codec-http2) before version 4.1.60.Final there is a vulnerability that enables request smuggling. If a Content-Length header is present in the original HTTP/2 request, the field is not validated by `Http2MultiplexHandler` as it is propagated up. This is fine as long as the request is not proxied through as HTTP/1.1. If the request comes in as an HTTP/2 stream, gets converted into the HTTP/1.1 domain objects (`HttpRequest`, `HttpContent`, etc.) via `Http2StreamFrameToHttpObjectCodec `and then sent up to the child channel\'s pipeline and proxied through a remote peer as HTTP/1.1 this may result in request smuggling. In a proxy case, users may assume the content-length is validated somehow, which is not the case. If the request is forwarded to a backend channel that is a HTTP/1.1 connection, the Content-Length now has meaning and needs to be checked. An attacker can smuggle requests inside the body as it gets downgraded from HTTP/2 to HTTP/1.1. For an example attack refer to the linked GitHub Advisory. Users are only affected if all of this is true: `HTTP2MultiplexCodec` or `Http2FrameCodec` is used, `Http2StreamFrameToHttpObjectCodec` is used to convert to HTTP/1.1 objects, and these HTTP/1.1 objects are forwarded to another remote peer. This has been patched in 4.1.60.Final As a workaround, the user can do the validation by themselves by implementing a custom `ChannelInboundHandler` that is put in the `ChannelPipeline` behind `Http2StreamFrameToHttpObjectCodec`.

Metrics

CVSS Version: 3.1 | Base Score: 5.9 MEDIUM
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

l➤ Exploitability Metrics:
    Attack Vector (AV)* NETWORK
    Attack Complexity (AC)* HIGH
    Privileges Required (PR)* NONE
    User Interaction (UI)* NONE
    Scope (S)* UNCHANGED

l➤ Impact Metrics:
    Confidentiality Impact (C)* NONE
    Integrity Impact (I)* HIGH
    Availability Impact (A)* NONE

Weakness Enumeration (CWE)

CWE-ID: CWE-444
CWE Name: CWE-444 Inconsistent Interpretation of HTTP Requests ( HTTP Request Smuggling )
Source: netty

Common Attack Pattern Enumeration and Classification (CAPEC)

CAPEC-ID:
CAPEC Description:


Source: NVD (National Vulnerability Database).