CVE-2023-28102 (published 2023-03-27T22:15Z)

discordrb is an implementation of the Discord API using Ruby. In discordrb before commit `91e13043ffa` the `encoder.rb` file unsafely constructs a shell string using the file parameter, which can potentially leave clients of discordrb vulnerable to command injection. The library is not directly exploitable: the exploit requires that some client of the library calls the vulnerable method with user input. However, if unsafe input reaches the library method, then an attacker can execute arbitrary shell commands on the host machine. Full impact will depend on the permissions of the process running the `discordrb` library and will likely not be total system access. This issue has been addressed in code, but a new release of the `discordrb` gem has not been uploaded to rubygems. This issue is also tracked as `GHSL-2022-094`.

CVSS v3 base score: 9.6, CRITICAL (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H)

Weakness information:
cwe_id: CWE-78
cwe_name: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
description: The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.
extended_description: 
		   This weakness can lead to a vulnerability in environments in which the attacker does not have direct access to the operating system, such as in web applications. Alternately, if the weakness occurs in a privileged program, it could allow the attacker to specify commands that normally would not be accessible, or to call alternate commands with privileges that the attacker does not have. The problem is exacerbated if the compromised process does not follow the principle of least privilege, because the attacker-controlled commands may run with special system privileges that increases the amount of damage.
            There are at least two subtypes of OS command injection:
               
				 The application intends to execute a single, fixed program that is under its own control. It intends to use externally-supplied inputs as arguments to that program. For example, the program might use system("nslookup [HOSTNAME]") to run nslookup and allow the user to supply a HOSTNAME, which is used as an argument. Attackers cannot prevent nslookup from executing. However, if the program does not remove command separators from the HOSTNAME argument, attackers could place the separators into the arguments, which allows them to execute their own program after nslookup has finished executing.
				 The application accepts an input that it uses to fully select which program to run, as well as which commands to use. The application simply redirects this entire command to the operating system. For example, the program might use "exec([COMMAND])" to execute the [COMMAND] that was supplied by the user. If the COMMAND is under attacker control, then the attacker can execute arbitrary commands or programs. If the command is being executed using functions like exec() and CreateProcess(), the attacker might not be able to combine multiple commands together in the same line.
               
            From a weakness standpoint, these variants represent distinct programmer errors. In the first variant, the programmer clearly intends that input from untrusted parties will be part of the arguments in the command to be executed. In the second variant, the programmer does not intend for the command to be accessible to any untrusted party, but the programmer probably has not accounted for alternate ways in which malicious attackers can provide input.
         
         

Fix information:
repo_url: https://github.com/shardlab/discordrb
commit_details: repo_url: https://github.com/shardlab/discordrb
author: Matthew Carey
author_date: 2023-03-08 15:33:54-05:00
msg: fix: switch popen to use an array invocation
repository: repo_url: https://github.com/shardlab/discordrb
repo_name: shardlab/discordrb
description: Discord API for Ruby 
repo_language: Ruby
owner: shardlab
file_changes: filename: encoder.rb
change_type: ModificationType.MODIFY
diff: @@ -77,7 +77,7 @@ module Discordrb::Voice
     # @param options [String] ffmpeg options to pass after the -i flag
     # @return [IO] the audio, encoded as s16le PCM
     def encode_file(file, options = '')
-      command = "#{ffmpeg_command} -loglevel 0 -i \"#{file}\" #{options} -f s16le -ar 48000 -ac 2 #{filter_volume_argument} pipe:1"
+      command = ffmpeg_command(input: file, options: options)
       IO.popen(command)
     end
 
@@ -87,14 +87,23 @@ module Discordrb::Voice
     # @param options [String] ffmpeg options to pass after the -i flag
     # @return [IO] the audio, encoded as s16le PCM
     def encode_io(io, options = '')
-      command = "#{ffmpeg_command} -loglevel 0 -i - #{options} -f s16le -ar 48000 -ac 2 #{filter_volume_argument} pipe:1"
+      command = ffmpeg_command(options: options)
       IO.popen(command, in: io)
     end
 
     private
 
-    def ffmpeg_command
-      @use_avconv ? 'avconv' : 'ffmpeg'
+    def ffmpeg_command(input: '-', options: null)
+      [
+        @use_avconv ? 'avconv' : 'ffmpeg',
+        '-loglevel', '0',
+        '-i', input,
+        '-f', 's16le',
+        '-ar', '48000',
+        '-ac', '2',
+        'pipe:1',
+        filter_volume_argument,
+      ].concat(options.split).reject {|segment| segment.nil? || segment == '' }
     end
 
     def filter_volume_argument

programming_language: Ruby