VYPR
Moderate severityNVD Advisory· Published Aug 4, 2023· Updated Oct 4, 2024

protocol-http1 HTTP Request/Response Smuggling vulnerability

CVE-2023-38697

Description

protocol-http1 provides a low-level implementation of the HTTP/1 protocol. RFC 9112 Section 7.1 defined the format of chunk size, chunk data and chunk extension. The value of Content-Length header should be a string of 0-9 digits, the chunk size should be a string of hex digits and should split from chunk data using CRLF, and the chunk extension shouldn't contain any invisible character. However, Falcon has following behaviors while disobey the corresponding RFCs: accepting Content-Length header values that have + prefix, accepting Content-Length header values that written in hexadecimal with 0x prefix, accepting 0x and + prefixed chunk size, and accepting LF in chunk extension. This behavior can lead to desync when forwarding through multiple HTTP parsers, potentially results in HTTP request smuggling and firewall bypassing. This issue is fixed in protocol-http1 v0.15.1. There are no known workarounds.

Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
protocol-http1RubyGems
< 0.15.10.15.1

Affected products

1

Patches

1
e11fc164fd2b

Strict validation of content length and chunk length. (#20)

https://github.com/socketry/protocol-http1Samuel WilliamsJul 30, 2023via ghsa
4 files changed · +140 5
  • lib/protocol/http1/body/chunked.rb+9 1 modified
    @@ -35,12 +35,20 @@ def close(error = nil)
     					super
     				end
     				
    +				VALID_CHUNK_LENGTH = /\A[0-9a-fA-F]+\z/
    +				
     				# Follows the procedure outlined in https://tools.ietf.org/html/rfc7230#section-4.1.3
     				def read
     					return nil if @finished
     					
    +					length, extensions = read_line.split(";", 2)
    +					
    +					unless length =~ VALID_CHUNK_LENGTH
    +						raise BadRequest, "Invalid chunk length: #{length.dump}"
    +					end
    +					
     					# It is possible this line contains chunk extension, so we use `to_i` to only consider the initial integral part:
    -					length = read_line.to_i(16)
    +					length = Integer(length, 16)
     					
     					if length == 0
     						@finished = true
    
  • lib/protocol/http1/connection.rb+4 2 modified
    @@ -398,10 +398,12 @@ def read_tunnel_body
     			HEAD = "HEAD"
     			CONNECT = "CONNECT"
     			
    +			VALID_CONTENT_LENGTH = /\A\d+\z/
    +			
     			def extract_content_length(headers)
     				if content_length = headers.delete(CONTENT_LENGTH)
    -					if length = Integer(content_length, exception: false) and length >= 0
    -						yield length
    +					if content_length =~ VALID_CONTENT_LENGTH
    +						yield Integer(content_length, 10)
     					else
     						raise BadRequest, "Invalid content length: #{content_length}"
     					end
    
  • test/protocol/http1/connection/bad.rb+125 0 added
    @@ -0,0 +1,125 @@
    +# frozen_string_literal: true
    +
    +# Released under the MIT License.
    +# Copyright, 2019-2023, by Samuel Williams.
    +
    +require 'protocol/http1/connection'
    +require 'connection_context'
    +
    +describe Protocol::HTTP1::Connection do
    +	include_context ConnectionContext
    +	
    +	def before
    +		super
    +		
    +		client.stream.write(input)
    +		client.stream.close
    +	end
    +	
    +	with "invalid hexadecimal content-length" do
    +		def input
    +			<<~HTTP.gsub("\n", "\r\n")
    +			POST / HTTP/1.1
    +			Host: a.com
    +			Content-Length: 0x10
    +			Connection: close
    +			
    +			0123456789abcdef
    +			HTTP
    +		end
    +		
    +		it "should fail to parse the request body" do
    +			expect do
    +				server.read_request
    +			end.to raise_exception(Protocol::HTTP1::BadRequest)
    +		end
    +	end
    +	
    +	with "invalid +integer content-length" do
    +		def input
    +			<<~HTTP.gsub("\n", "\r\n")
    +			POST / HTTP/1.1
    +			Host: a.com
    +			Content-Length: +16
    +			Connection: close
    +			
    +			0123456789abcdef
    +			HTTP
    +		end
    +		
    +		it "should fail to parse the request body" do
    +			expect do
    +				server.read_request
    +			end.to raise_exception(Protocol::HTTP1::BadRequest)
    +		end
    +	end
    +	
    +	with "invalid -integer content-length" do
    +		def input
    +			<<~HTTP.gsub("\n", "\r\n")
    +			POST / HTTP/1.1
    +			Host: a.com
    +			Content-Length: -16
    +			Connection: close
    +			
    +			0123456789abcdef
    +			HTTP
    +		end
    +		
    +		it "should fail to parse the request body" do
    +			expect do
    +				server.read_request
    +			end.to raise_exception(Protocol::HTTP1::BadRequest)
    +		end
    +	end
    +	
    +	with "invalid hexidecimal chunk size" do
    +		def input
    +			<<~HTTP.gsub("\n", "\r\n")
    +			POST / HTTP/1.1
    +			Host: a.com
    +			Transfer-Encoding: chunked
    +			Connection: close
    +			
    +			0x10
    +			0123456789abcdef
    +			0
    +			HTTP
    +		end
    +		
    +		it "should fail to parse the request body" do
    +			authority, method, target, version, headers, body = server.read_request
    +			
    +			expect(body).to be_a(Protocol::HTTP1::Body::Chunked)
    +			
    +			expect do
    +				body.read
    +			end.to raise_exception(Protocol::HTTP1::BadRequest)
    +		end
    +	end
    +	
    +	with "invalid +integer chunk size" do
    +		def input
    +			<<~HTTP.gsub("\n", "\r\n")
    +			POST / HTTP/1.1
    +			Host: a.com
    +			Transfer-Encoding: chunked
    +			Connection: close
    +			
    +			+10
    +			0123456789abcdef
    +			0
    +			HTTP
    +		end
    +		
    +		it "should fail to parse the request body" do
    +			authority, method, target, version, headers, body = server.read_request
    +			
    +			expect(body).to be_a(Protocol::HTTP1::Body::Chunked)
    +			
    +			expect do
    +				body.read
    +			end.to raise_exception(Protocol::HTTP1::BadRequest)
    +		end
    +	end
    +end
    
  • test/protocol/http1/connection.rb+2 2 modified
    @@ -208,15 +208,15 @@
     		
     		with "HEAD" do
     			it "can read length of head response" do
    -				body = client.read_response_body("HEAD", 200, {'content-length' => 3773})
    +				body = client.read_response_body("HEAD", 200, {'content-length' => '3773'})
     				
     				expect(body).to be_a ::Protocol::HTTP::Body::Head
     				expect(body.length).to be == 3773
     				expect(body.read).to be_nil
     			end
     			
     			it "ignores zero length body" do
    -				body = client.read_response_body("HEAD", 200, {'content-length' => 0})
    +				body = client.read_response_body("HEAD", 200, {'content-length' => '0'})
     				
     				expect(body).to be_nil
     			end
    

Vulnerability mechanics

Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

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