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sip fuzz request


Perform a SIP request fuzzing attack

What it does

Perform a SIP fuzzing test on specific SIP requests. This tool allows testers to check the robustness of the SIP parser and SIP stack by sending mutated SIP messages to the target system.

Tool functionality

The sip fuzz request module helps identify unknown security issues using fuzzing techniques. It mutates SIP messages before they are sent to the target server by making use of the mutation engine that is specified. By default it uses radamsa, but the zzuf mutator can also be used as a mutation engine. For details about getting these third-party mutators setup on your system, please follow the installation page.

In the case of most SIP messages, the functionality is rather simple: send malformed SIP messages as fast as possible. In the case of INVITE messages, extra behaviour is implemented to trigger different conditions. A random user/extension is generated for each request sent by default.

The fuzzer works by repeating the following steps:

  1. Build the SIP message depending on the SIP message chosen and the corresponding template
  2. Generate the correct values for each SIP header (e.g. a random branch and call-id)
  3. Pass the SIP message to the mutator engine
  4. Send the mutated SIP message to the target
  5. Handle responses according to normal SIP logic just like the sip utils call utility

When credentials are passed using the relevant flag, the first unauthenticated SIP message is not passed to the mutator engine. This allows authenticated messages to be fuzzed. By default, all fuzzing methods (i.e. whole message, specific headers and so on) are used randomly but this behaviour can be changed by specifying a value to the fuzz flag. A tester can specify which SIP header is mutated by making use of the value header:specific-header, where specific header is a valid SIP header that is to be targeted. Other options are available to, for example, fuzz only the SIP message body or request line. Additionally, all SIP methods supported by this module are used randomly unless the method flag is used to specify an individual SIP method.

A prober is switched on by default, which will send a SIP message that is known to elicit a response from the target system. This is used to monitor the system and tell if the system starts missing messages or stops responding at all. This is done by sending the same message that is used to initiate the SIP fuzzing exercise. The prober should record the response code so that if it later changes (e.g. from a 200 or 404 to a 5XX server error), it can report this change. If the prober starts missing responses, these get logged as a non-fatal error.

Video demonstration

sipvicious sip fuzz request

Command format

sipvicious sip fuzz request <target1 [target2 [target3 ...]]> [flags]


      --auth-config strings   Specify SIP authentication configuration. See documentation for details e.g. algorithm:sha-256
      --caller-mode strings   Specify how to behave when the method being fuzzed is INVITE; format: action or action:duration; (ignore|hangup-trying|hangup-ringing|hangup-call|never-hangup); default: ignore
      --close-conn            Close the connection after sending each message, instead of keeping it alive
  -c, --conn-count int        Number of sockets to use (per target) (default 30)
  -u, --credentials string    Set the username and password in the following format: username:password[:realm] (e.g. 1000:test123:snowflake). Realm is optional
  -D, --domain string         Override domain name for the SIP address
  -e, --extension string      Specify a target extension or SIP URI in the To address; if not specified, a random numeric extension is used when required
  -f, --from string           Specify a from extension or SIP URI to set the From address; if not specified, a random numeric extension is used
      --fuzz-mode string      Specify which part to fuzz; format: part:value; (header|message|body|request-line); e.g. header:Via; see full documentation for details
      --max-requests int      Set the maximum number of requests to send
      --mutator string        Specify the mutator to use (radamsa|zzuf|none) (default "radamsa")
      --no-prober             Turn off target monitoring that normally sends ping messages to check for errors or timeouts
      --rate string           Specify how many packets to send for each period of time; format: packets/duration; e.g. 100/30ms
      --register              Maintain a registration; requires -u

Flags inherited from parent commands

      --ca-cert string       TLS CA Certificate
      --client-cert string   TLS client certificate
      --client-key string    TLS client private key
  -C, --config string        configuration file to use (may be JSON, TOML or YAML)
      --debug                set log level to debug
  -T, --duration duration    Stop the tool after a certain amount of time; e.g. 30s
      --logfile string       specify a log filename
      --results string       specify the filename for the result output, defaults to standard output. See documentation for information on file extension meanings
      --srtp string          Specify if either none, dtls or sdes to enforce SRTP for calls; format: method or method:parameters; see full documentation for details (default "none")
      --templates string     Directory to search for template overrides (default ".")
      --tls-key-log string   TLS key log


sipvicious sip fuzz request udp://target:5060 --method invite --register -u 1000:test
sipvicious sip fuzz request tcp://target:5060 --rate 100/1s -m REGISTER
sipvicious sip fuzz request tls://target:5061 --duration 10m 
sipvicious sip fuzz request udp://target:5060 -T5s

Advanced examples

# fuzz the invite request while maintaining a registration using the credentials given
sipvicious sip fuzz request -m invite -u 1000:1500 udp:// --register

# bypass network security rate limiting by slowing down and prolonging the attack
sipvicious sip fuzz request udp:// -c 100 --duration 100m --rate 1/20ms -e 2000

# fuzz the publish request
sipvicious sip fuzz request udp:// -e 2000 -m publish

Exit codes

40A security issue is raised when the prober detects SIP-level or network-level errors
30A network connectivity issue is raised when the connection fails before the attack is started

Full flag documentation

Flag: --auth-config

Specify SIP authentication configuration. This flag accepts the following values:

  • algorithm:value where value may be md5, md5-sess, sha-256, sha-256-sess, sha-512-256 or sha-512-256-sess. This value will force the tool to calculate the authorization response based on the first WWW-Authenticate or Proxy-Authenticate header field that matches this algorithm. If no match is found then the first WWW-Authenticate or Proxy-Authenticate header is selected.

Flag: --ca-cert

The CA cert can be passed when making use of client certificate authentication. The file should be formatted as PEM.

Flag: --caller-mode

The flag caller-mode allows one to specify how to behave during an INVITE fuzzing session. The value of this flag could be one of the following actions:

  • ignore which does not wait for SIP INVITE responses; this is the default
  • hangup-trying which sends a CANCEL as soon as a 100 Trying message is received
  • hangup-ringing which sends a CANCEL as soon as a 180 Ringing is received
  • hangup-call which hangs up (by sending a BYE) when a call is picked up (i.e. when a 200 OK is received)
  • never-hangup which handles the call flow normally without hanging up

Additionally, the action value may be preceded by a colon and a duration value. This duration should be specified when the action should be taken after a specific time (e.g. 2s or 300ms). For example, hangup-ringing:300ms.

Flag: --client-cert

The client certificate must be passed when making use of client certificate authentication. The file should be formatted as PEM.

Flag: --client-key

The client key must be passed when making use of client certificate authentication. The file should be formatted as PEM.

Flag: --close-conn

The default connection behaviour is to try to keep all connections alive or, in the case of UDP, to reuse the same socket. This flag overrides this behaviour so that the connection is closed after each message is sent. This can uncover vulnerabilities related to socket handling in relation to SIP signalling.

Flag: -C, --config

Specify a configuration file which may be a JSON, TOML and YAML config format. To get the default settings and figure out which settings are available, one may run the sipvicious utils dump config command. This is typically used to create a template configuration that can then be edited as need be.

These settings may be overwritten when the corresponding flag is explicitly set, if one is present.

Flag: -c, --conn-count

The conn-count allows setting of how many sockets should be used concurrently to spread out the attack.

Flag: -u, --credentials

Specify valid credentials so that SIP fuzzing can be done authenticated. The following format is used username:password (e.g. 1000:test123). When not specified, if required, the tool will send fake challenge responses.

Additionally, a realm may be specified as a third parameter (e.g. 1000:test123:snowflake).

Note: This does not set the correct SIP To and From headers, which might cause authorization checks to fail. Set the -e and --from flags if this is required.

Flag: --debug

Tells the logger to print out debug messages.

Flag: -D, --domain

A domain name can be specified so that the SIP URI contains that particular domain rather than the one specified as the target. This is useful for targets that expect a particular domain name.

Flag: -T, --duration

Specify the maximum duration of the attack so that it stops after a certain time. Examples include:

  • 30s
  • 10m
  • 24h

Flag: -e, --extension

This flag allows users to target a particular extension, overriding the default behaviour of targeting random extensions. The value can be either just the SIP extension/username (e.g. 1234) or a SIP URI (e.g.

Flag: -f, --from

This flag allows users to set the From address, overriding the default behaviour of setting a random extension or the username in the credentials when one is provided. The value can be either just the SIP extension/username (e.g. 1234) or a SIP URI (e.g.

Flag: --fuzz-mode

The flag fuzz-mode allows one to specify which part of the SIP message to mutate. The value of this flag could be one of the following:

  • message which is default and mutates the whole SIP message
  • header which only mutates one header at a time
  • body which mutates the whole SIP body
  • request-line which only mutates the first line of the SIP request

Additionally, when header is specified as value, it can take a header name which is preceded with a colon. For example, the following value would fuzz the Via header: header:via.

By default, all fuzzing methods are used randomly when the value is not set.

Flag: --logfile

When the logfile flag is specified, a log file is created in the location specified and logs are generated in this file instead of being sent to standard output. If the filename ends with a .json file extension, then the output format is in JSON, otherwise it defaults to text format.

Flag: --max-requests

Specify the maximum number of messages to send before stopping the attack.

Flag: -m, --method

The SIP fuzz request tool supports the following SIP methods:

  • ACK
  • BYE
  • INFO

In the case of INVITE messages, the caller-mode method specifies extra parameters that are only specific to this method. By default, all SIP methods are used randomly fuzzed when the value is not set.

Flag: --mutator

Choose the mutation engine to use. Currently supported are the following:

The none mutator can be specified for debugging reasons, for example, to ensure that the SIP messages are generated correctly. When using this value, no fuzzing is actually done.

Flag: --no-prober

Switches off the default prober which sends a SIP message to detect errors and issues during an attack.

Flag: --rate

Rate allows one to limit the attack below a certain rate. If the value is 100/30ms, that means that 100 packets should be spread out evenly across 30 milliseconds across all the connections per target.

Flag: --register

Register requires credentials to be passed so that a REGISTER message is sent to authenticate with a registrar server before starting the attack. The registration is maintained as per SIP standards, so that authentication does not time out.

Flag: --results

When the results flag is specified, upon completing the test, it outputs the results to the specified filename. The format for this output file is text unless the filename ends with a .json file extension. In that case, the result output is that of JSON.

The schema for the JSON output for this submodule can be found here.

Flag: --srtp

The srtp flag when specified, allows users to set the SRTP mode. By default, outgoing calls do not make use of SRTP, while incoming calls automatically handle SRTP depending on the SDP body of the incoming INVITE message. When the srtp flag is set to none, incoming calls do not make use of SRTP, regardless of the SDP body in an incoming INVITE. The srtp mode can also be either dtls or sdes. In both dtls and sdes modes, the parameters are not required and will be generated randomly as need be.

Options for both dtls and sdes mode may be passed after a colon. For example:

  • --srtp dtls:cert.crt:cert.key[:ca.crt] where the first argument after the mode (dtls) is the public certificate cert.crt, then the private key cert.key and finally, the optional certificate authority file ca.crt
  • --srtp sdes:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj where the argument is the base64 encoded cryptographic master key appended with the master salt.

Note that in the case of sdes key, the master key needs to be a valid length, which is 30 octets, for the default crypto-suite AES_CM_128_HMAC_SHA1_80.

Flag: --templates

Allows one to set the template directory which is used to load (or save) the SIP templates.

To get the default SIP templates, make use of the sipvicious sip utils dump templates command.

Flag: --tls-key-log

The TLS key log creates a file with the TLS key that can then be used to decrypt the TLS stream in tools that support it, such as Wireshark.

JSON schema

The following is the JSON schema for the JSON output of this tool:

  "type": "object",
  "properties": {
    "status": {
      "type": "object",
      "properties": {
        "returncode": { "type": "integer" },
        "description": { "type": "string" }
    "targets": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "target": { "type": "string" },
          "status": {
            "type": "object",
            "properties": {
              "returncode": { "type": "integer" },
              "description": { "type": "string" }
          "results": {
            "type": "object",
            "properties": {
          "issues": {
            "type": "object",
            "properties": {