Fuzz introspector
For issues and ideas: https://github.com/ossf/fuzz-introspector/issues
Project coverage

Table of contents

Project overview: ipykernel
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_serialization_roundtrip
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Fuzzer: fuzz_unpack_roundtrip
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Analyses and suggestions
Optimal target analysis
Remaining optimal interesting functions
All functions overview
Fuzz engine guidance
/src/fuzz_serialization_roundtrip.py
Dictionary
Fuzzer function priority
/src/fuzz_unpack_roundtrip.py
Dictionary
Fuzzer function priority
Runtime coverage analysis
Complex functions with low coverage
Files and Directories in report
Files in report
Directories in report
Metadata section
Report generation date: 2025-07-12

Project overview: ipykernel

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
3.0%
14 / 536
Cyclomatic complexity statically reachable by fuzzers
3.0%
49 / 1765
Runtime code coverage of functions
2.0%
12 / 536

Fuzzers overview

Fuzzer Fuzzer filename Functions Reached Functions unreached Fuzzer depth Files reached Basic blocks reached Cyclomatic complexity Details
fuzz_serialization_roundtrip /src/fuzz_serialization_roundtrip.py 45 1659 5 4 20 139 fuzz_serialization_roundtrip.py
fuzz_unpack_roundtrip /src/fuzz_unpack_roundtrip.py 53 1592 5 4 20 163 fuzz_unpack_roundtrip.py

Project functions overview

The following table shows data about each function in the project. The functions included in this table correspond to all functions that exist in the executables of the fuzzers. As such, there may be functions that are from third-party libraries.

For further technical details on the meaning of columns in the below table, please see the Glossary .

Func name Functions filename Args Function call depth Reached by Fuzzers Runtime reached by Fuzzers Combined reached by Fuzzers Fuzzers runtime hit Func lines hit % I Count BB Count Cyclomatic complexity Functions reached Reached by functions Accumulated cyclomatic complexity Undiscovered complexity

Fuzzer details

Fuzzer: fuzz_serialization_roundtrip

Call tree

The calltree shows the control flow of the fuzzer. This is overlaid with coverage information to display how much of the potential code a fuzzer can reach is in fact covered at runtime. In the following there is a link to a detailed calltree visualisation as well as a bitmap showing a high-level view of the calltree. For further information about these topics please see the glossary for full calltree and calltree overview

Full calltree

Call tree overview bitmap:

The distribution of callsites in terms of coloring is
Color Runtime hitcount Callsite count Percentage
red 0 89 100.%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 0 0.0%
All colors 89 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
88 0 EP call site: 00000 ipykernel.serialize.serialize_object

Runtime coverage analysis

Covered functions
94
Functions that are reachable but not covered
43
Reachable functions
45
Percentage of reachable functions covered
4.44%
NB: The sum of covered functions and functions that are reachable but not covered need not be equal to Reachable functions . This is because the reachability analysis is an approximation and thus at runtime some functions may be covered that are not included in the reachability analysis. This is a limitation of our static analysis capabilities.
Warning: The number of covered functions are larger than the number of reachable functions. This means that there are more functions covered at runtime than are extracted using static analysis. This is likely a result of the static analysis component failing to extract the right call graph or the coverage runtime being compiled with sanitizers in code that the static analysis has not analysed. This can happen if lto/gold is not used in all places that coverage instrumentation is used.
Function name source code lines source lines hit percentage hit

Files reached

filename functions hit
/ 1
...fuzz_serialization_roundtrip 8
ipykernel.serialize 25
ipykernel.pickleutil 17

Fuzzer: fuzz_unpack_roundtrip

Call tree

The calltree shows the control flow of the fuzzer. This is overlaid with coverage information to display how much of the potential code a fuzzer can reach is in fact covered at runtime. In the following there is a link to a detailed calltree visualisation as well as a bitmap showing a high-level view of the calltree. For further information about these topics please see the glossary for full calltree and calltree overview

Full calltree

Call tree overview bitmap:

The distribution of callsites in terms of coloring is
Color Runtime hitcount Callsite count Percentage
red 0 120 100.%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 0 0.0%
All colors 120 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
119 0 EP call site: 00000 ipykernel.serialize.pack_apply_message

Runtime coverage analysis

Covered functions
93
Functions that are reachable but not covered
51
Reachable functions
53
Percentage of reachable functions covered
3.77%
NB: The sum of covered functions and functions that are reachable but not covered need not be equal to Reachable functions . This is because the reachability analysis is an approximation and thus at runtime some functions may be covered that are not included in the reachability analysis. This is a limitation of our static analysis capabilities.
Warning: The number of covered functions are larger than the number of reachable functions. This means that there are more functions covered at runtime than are extracted using static analysis. This is likely a result of the static analysis component failing to extract the right call graph or the coverage runtime being compiled with sanitizers in code that the static analysis has not analysed. This can happen if lto/gold is not used in all places that coverage instrumentation is used.
Function name source code lines source lines hit percentage hit

Files reached

filename functions hit
/ 1
...fuzz_unpack_roundtrip 9
ipykernel.serialize 35
ipykernel.pickleutil 16

Analyses and suggestions

Optimal target analysis

Remaining optimal interesting functions

The following table shows a list of functions that are optimal targets. Optimal targets are identified by finding the functions that in combination, yield a high code coverage.

Func name Functions filename Arg count Args Function depth hitcount instr count bb count cyclomatic complexity Reachable functions Incoming references total cyclomatic complexity Unreached complexity
ipykernel.kernelapp.IPKernelApp.initialize ipykernel.kernelapp 2 ['N/A', 'N/A'] 6 0 22 3 4 103 0 329 311
ipykernel.debugger.Debugger.process_request ipykernel.debugger 2 ['N/A', 'N/A'] 4 0 5 7 6 87 1 268 226
ipykernel.ipkernel.IPythonKernel.do_execute ipykernel.ipkernel 8 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 2 0 8 8 6 69 0 213 195
ipykernel.kernelbase.Kernel.execute_request ipykernel.kernelbase 4 ['N/A', 'N/A', 'N/A', 'N/A'] 3 0 9 7 6 40 0 131 98
ipykernel.inprocess.client.InProcessKernelClient._dispatch_to_kernel ipykernel.inprocess.client 2 ['N/A', 'N/A'] 2 0 5 2 4 32 8 100 91
ipykernel.ipkernel.IPythonKernel.__init__ ipykernel.ipkernel 2 ['N/A', 'N/A'] 3 0 6 4 5 29 0 92 71
ipykernel.kernelspec.InstallIPythonKernelSpecApp.start ipykernel.kernelspec 1 ['N/A'] 4 0 13 3 4 24 0 81 66
ipykernel.subshell_manager.SubshellManager._process_control_request ipykernel.subshell_manager 2 ['N/A', 'N/A'] 4 0 3 3 4 32 0 100 64
ipykernel.ipkernel.IPythonKernel.do_is_complete ipykernel.ipkernel 2 ['N/A', 'N/A'] 1 0 1 2 4 20 0 64 61
ipykernel.zmqshell.ZMQDisplayPublisher.publish ipykernel.zmqshell 5 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 3 0 4 3 4 40 0 129 61

Implementing fuzzers that target the above functions will improve reachability such that it becomes:

Functions statically reachable by fuzzers
18.0%
95 / 536
Cyclomatic complexity statically reachable by fuzzers
19.0%
336 / 1765

All functions overview

If you implement fuzzers for these functions, the status of all functions in the project will be:

Func name Functions filename Args Function call depth Reached by Fuzzers Runtime reached by Fuzzers Combined reached by Fuzzers Fuzzers runtime hit Func lines hit % I Count BB Count Cyclomatic complexity Functions reached Reached by functions Accumulated cyclomatic complexity Undiscovered complexity

Fuzz engine guidance

This sections provides heuristics that can be used as input to a fuzz engine when running a given fuzz target. The current focus is on providing input that is usable by libFuzzer.

/src/fuzz_serialization_roundtrip.py

Dictionary

Use this with the libFuzzer -dict=DICT.file flag


/src/fuzz_unpack_roundtrip.py

Dictionary

Use this with the libFuzzer -dict=DICT.file flag


Runtime coverage analysis

This section shows analysis of runtime coverage data.

For futher technical details on how this section is generated, please see the Glossary .

Complex functions with low coverage

Func name Function total lines Lines covered at runtime percentage covered Reached by fuzzers
ipyparallel.serialize.canning.uncan 302 68 22.51% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
traitlets.HasTraits.put_nowait 61 21 34.42% ['fuzz_serialization_roundtrip']
IPython.core.application.BaseIPythonApplication.session.flush 254 87 34.25% ['fuzz_serialization_roundtrip']
f.write 505 67 13.26% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
subprocess.Popen 243 67 27.57% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
jupyter_client.session.Session.put_nowait 449 130 28.95% ['fuzz_serialization_roundtrip']
jupyter_core.paths.jupyter_runtime_dir 460 62 13.47% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
zmq.PUSH.shell_stream.recv_multipart 44 22 50.0% ['fuzz_serialization_roundtrip']
socket.send 324 111 34.25% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
io.TextIOBase._parent_header.get 64 19 29.68% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
jupyter_client.connect.ConnectionFileMixin.shell.InteractiveTB.stb2text 297 74 24.91% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
app.shell.set_completer_frame 235 73 31.06% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
logging.error 67 20 29.85% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
handler.setFormatter 77 24 31.16% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
logger.error 117 20 17.09% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
asyncio.set_event_loop 94 46 48.93% ['fuzz_serialization_roundtrip']
loop.shutdown_asyncgens 287 103 35.88% ['fuzz_serialization_roundtrip']
jupyter_client.localinterfaces.localhost 202 45 22.27% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
arch.startswith 89 23 25.84% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
ipykernel.iostream.OutStream.__init__ 52 2 3.846% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
name.rpartition 114 11 9.649% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
buffer.close 824 144 17.47% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
ipykernel.kernelbase.Kernel.dispatch_shell 58 0 0.0% []
ipykernel.kernelbase.Kernel.execute_request 40 0 0.0% []
ipykernel.kernelbase.Kernel._input_request 32 0 0.0% []
comm.close 149 39 26.17% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
cmd.rstrip 236 43 18.22% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
future.add_done_callback 404 73 18.06% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
zmq.eventloop.zmqstream.ZMQStream.background_socket.shell_stream.recv_multipart 278 74 26.61% ['fuzz_serialization_roundtrip']
IPython.core.interactiveshell.InteractiveShell.shell_stream.recv_multipart 1663 345 20.74% ['fuzz_serialization_roundtrip']
IPython.utils.tokenutil.token_at_cursor 101 18 17.82% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
IPython.core.completer.rectify_completions 1377 282 20.47% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
inspect.isawaitable 913 483 52.90% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
tornado.queues.Queue 153 56 36.60% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
psutil.virtual_memory 949 236 24.86% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
re.match 199 44 22.11% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
packaging.version.Version 85 34 40.0% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
s.encode 111 43 38.73% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
tornado.locks.Event.wait 162 56 34.56% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
result.get 620 112 18.06% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
IPython.core.displayhook.DisplayHook.hb_channel_class 174 38 21.83% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
IPython.core.displaypub.DisplayPublisher.hb_channel_class 53 21 39.62% ['fuzz_serialization_roundtrip']
IPython.core.magic.Magics.shell.getoutput 271 110 40.59% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
IPython.utils.openpy.read_py_file 47 12 25.53% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
IPython.core.page.as_hook 177 28 15.81% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
ipyparallel.bind_kernel 44 13 29.54% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
IPython.utils.process.arg_split 32 13 40.62% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
jupyter_client.kernelspec.KernelSpecManager.install_kernel_spec 216 68 31.48% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
parser.parse_args 817 128 15.66% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
zmq.log.handlers.PUBHandler.__init__ 67 26 38.80% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
jupyter_client.client.KernelClient.session.recv 338 82 24.26% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
jupyter_core.utils.run_sync 106 45 42.45% ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip']
zmq.DEALER.shell_stream.recv_multipart 44 22 50.0% ['fuzz_unpack_roundtrip']

Files and Directories in report

This section shows which files and directories are considered in this report. The main reason for showing this is fuzz introspector may include more code in the reasoning than is desired. This section helps identify if too many files/directories are included, e.g. third party code, which may be irrelevant for the threat model. In the event too much is included, fuzz introspector supports a configuration file that can exclude data from the report. See the following link for more information on how to create a config file: link

Files in report

Source file Reached by Covered by
[] []
packaging [] []
logging [] []
_pydevd_bundle [] []
ipykernel.subshell [] []
ipykernel.parentpoller [] []
itertools [] []
pickle [] []
trio [] []
typing [] []
zmq [] []
atheris [] []
argparse [] []
ipykernel.ipkernel [] []
json [] []
IPython [] []
ipykernel.shellchannel [] []
ipykernel.inprocess.ipkernel [] []
ipykernel.comm [] []
ipykernel.subshell_manager [] []
comm [] []
ipykernel.inprocess.blocking [] []
platform [] []
ipykernel.pylab [] []
ipykernel.trio_runner [] []
ipykernel.pickleutil ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip'] []
ipykernel.control [] []
gc [] []
warnings [] []
ipykernel.thread [] []
traceback [] []
ipykernel.pylab.config [] []
signal [] []
ctypes [] []
socket [] []
ipykernel.gui [] []
jupyter_core [] []
appnope [] []
ipykernel.zmqshell [] []
ipykernel.embed [] []
uuid [] []
datetime [] []
ipykernel.gui.gtkembed [] []
threading [] []
wx [] []
ipykernel.inprocess.constants [] []
ipykernel.kernelbase [] []
shutil [] []
gobject [] []
ipykernel.socket_pair [] []
ipykernel.jsonutil [] []
...fuzz_serialization_roundtrip ['fuzz_serialization_roundtrip'] []
os [] []
traitlets [] []
operator [] []
gi [] []
ipykernel.inprocess.manager [] []
contextvars [] []
numpy [] []
ipykernel.inprocess.client [] []
ipykernel.compiler [] []
queue [] []
subprocess [] []
ipykernel.__main__ [] []
[] []
asyncio [] []
ipykernel [] []
_thread [] []
ipykernel.inprocess.channels [] []
jupyter_client [] []
...fuzz_unpack_roundtrip ['fuzz_unpack_roundtrip'] []
ipykernel.heartbeat [] []
types [] []
ipykernel.log [] []
io [] []
math [] []
binascii [] []
sys [] []
ipyparallel [] []
ipykernel.inprocess.socket [] []
ipykernel.debugger [] []
pathlib [] []
collections [] []
psutil [] []
copy [] []
ipykernel._version [] []
ipykernel.serialize ['fuzz_serialization_roundtrip', 'fuzz_unpack_roundtrip'] []
ipykernel.gui.gtk3embed [] []
time [] []
re [] []
ipykernel.iostream [] []
ipykernel.kernelspec [] []
ipykernel.connect [] []
ipykernel.kernelapp [] []
atexit [] []
faulthandler [] []
ipykernel.comm.comm [] []
tornado [] []
inspect [] []
ipykernel.datapub [] []
ipykernel.pylab.backend_inline [] []
ipykernel.displayhook [] []
nest_asyncio [] []
gtk [] []
functools [] []
tempfile [] []
tkinter [] []
ipykernel.eventloops [] []
ipykernel.comm.manager [] []
ipykernel._eventloop_macos [] []
ipykernel.inprocess [] []

Directories in report

Directory

Metadata section

This sections shows the raw data that is used to produce this report. This is mainly used for further processing and developer debugging.

Fuzzer Calltree file Program data file Coverage file
fuzz_serialization_roundtrip fuzzerLogFile-fuzz_serialization_roundtrip.data fuzzerLogFile-fuzz_serialization_roundtrip.data.yaml all_cov.json
fuzz_unpack_roundtrip fuzzerLogFile-fuzz_unpack_roundtrip.data fuzzerLogFile-fuzz_unpack_roundtrip.data.yaml all_cov.json