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

Table of contents

Project overview: bs4
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: bs4_fuzzer
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/bs4_fuzzer.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: 2025-10-23

Project overview: bs4

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
7.00%
37 / 543
Cyclomatic complexity statically reachable by fuzzers
9.0%
170 / 1927
Runtime code coverage of functions
55.0%
298 / 543

Warning: The number of runtime covered functions are larger than the number of reachable functions. This means that Fuzz Introspector found there are more functions covered at runtime than what is considered reachable based on the static analysis. This is a limitation in the analysis as anything covered at runtime is by definition reachable by the fuzzers.
This is likely due to a limitation in the static analysis. In this case, the count of functions covered at runtime is the true value, which means this is what should be considered "achieved" by the fuzzer.

Use the project functions table below to query all functions that were not covered at runtime.

Fuzzers overview

Fuzzer Fuzzer filename Functions Reached Functions unreached Fuzzer depth Files reached Basic blocks reached Cyclomatic complexity Details
bs4_fuzzer /src/bs4_fuzzer.py 228 838 6 7 165 746 bs4_fuzzer.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 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: bs4_fuzzer

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 0 258 68.9%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 116 31.0%
All colors 374 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
79 228 bs4.element.SoupStrainer._matches call site: 00228 bs4.element.SoupStrainer._matches
22 34 bs4.BeautifulSoup.__init__ call site: 00034 bs4.BeautifulSoup._check_markup_is_url
20 315 bs4.element.Tag.decode call site: 00315 bs4.element.PageElement.formatter_for_name
17 149 bs4.element.SoupStrainer._matches call site: 00149 bs4.element.SoupStrainer._normalize_search_value
13 345 bs4.element.Tag.decode_contents call site: 00345 bs4.element.Tag.decode
12 10 bs4.BeautifulSoup.__init__ call site: 00010 bs4.builder.TreeBuilderRegistry.lookup
12 95 bs4.element.SoupStrainer._normalize_search_value call site: 00095 html5lib.treebuilders.base.Node.next_sibling.prefix.name.string.decode
9 135 bs4.element.SoupStrainer.search call site: 00135 bs4.element.SoupStrainer.search
8 86 ...bs4_fuzzer.TestOneInput call site: 00086 bs4.element.PageElement._find_all
8 365 bs4.element.Tag.decode call site: 00365 bs4.element.Tag.encode
7 124 bs4.element.PageElement._find_all call site: 00124 bs4.element.ResultSet.__init__
5 57 bs4.BeautifulSoup._check_markup_is_url call site: 00057 bs4.BeautifulSoup.reset

Runtime coverage analysis

Covered functions
321
Functions that are reachable but not covered
199
Reachable functions
228
Percentage of reachable functions covered
12.72%
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
...bs4_fuzzer 8
bs4 38
bs4.builder 7
bs4.element 183
bs4.formatter 6
bs4.dammit 1

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
bs4.element.Tag.select bs4.element 5 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 10 0 1 3 4 155 1 598 577
bs4.dammit.EncodingDetector.encodings bs4.dammit 1 ['N/A'] 2 0 7 8 6 17 0 60 48
bs4.dammit.UnicodeDammit.__init__ bs4.dammit 8 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 4 0 2 6 5 17 1 59 41
bs4.element.PageElement.insert bs4.element 3 ['N/A', 'N/A', 'N/A'] 3 0 4 14 9 11 13 51 39

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

Functions statically reachable by fuzzers
25.0%
134 / 543
Cyclomatic complexity statically reachable by fuzzers
32.0%
611 / 1927

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 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/bs4_fuzzer.py

Dictionary

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


Fuzzer function priority

Use one of these functions as input to libfuzzer with flag: -focus_function name 

-focus_function=['bs4.element.SoupStrainer._matches', 'bs4.BeautifulSoup.__init__', 'bs4.element.Tag.decode', 'bs4.element.Tag.decode_contents', 'bs4.element.SoupStrainer._normalize_search_value', 'bs4.element.SoupStrainer.search', '...bs4_fuzzer.TestOneInput']

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
bs4.element.PageElement.insert 60 23 38.33% []
bs4.element.Tag.__init__ 39 16 41.02% ['bs4_fuzzer']
bs4.element.SoupStrainer._matches 48 20 41.66% ['bs4_fuzzer']
bs4.builder._html5lib.TreeBuilderForHtml5lib.testSerializer.serializeElement 36 1 2.777% []
bs4.builder._html5lib.Element.reparentChildren 33 2 6.060% []
bs4.builder._htmlparser.parse_starttag 41 0 0.0% []
html.entities.codepoint2name.items 991 38 3.834% []
bs4.dammit.chardet_dammit 327 150 45.87% []
soupsieve.css_match._Match.match_nth 64 6 9.375% []
soupsieve.css_match._Match.match_indeterminate.get_parent_form 42 3 7.142% []
soupsieve.css_match._Match.match_lang 60 2 3.333% []
soupsieve.css_match._Match.match_dir 46 1 2.173% []
soupsieve.css_match._Match.match_range 35 0 0.0% []
soupsieve.css_match._Match.match_selectors 44 2 4.545% []
soupsieve.css_match.SoupSieve.__repr__ 49 25 51.02% []
m.start 625 219 35.04% []
x.lower 584 268 45.89% []
s.freeze 93 45 48.38% []
soupsieve.css_parser.CSSParser.parse_pseudo_class 67 20 29.85% []
soupsieve.css_parser.CSSParser.parse_pseudo_nth 33 13 39.39% []
soupsieve.css_parser.CSSParser.parse_selectors 102 42 41.17% []

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
[] []
logging [] []
cchardet [] []
bs4.element ['bs4_fuzzer'] []
soupsieve.css_match [] []
pstats [] []
copy [] []
sys [] []
html5lib [] []
collections [] []
unicodedata [] []
lxml [] []
unittest [] []
tempfile [] []
soupsieve.util [] []
bs4.builder ['bs4_fuzzer'] []
[] []
atheris [] []
io [] []
soupsieve.css_types [] []
bs4.testing [] []
time [] []
html [] []
copyreg [] []
soupsieve [] []
warnings [] []
codecs [] []
bs4 ['bs4_fuzzer'] []
traceback [] []
bs4.builder._html5lib [] []
os [] []
cProfile [] []
functools [] []
chardet [] []
soupsieve.css_parser [] []
bs4.diagnose [] []
random [] []
datetime [] []
re [] []
bs4.builder._htmlparser [] []
bs4.formatter ['bs4_fuzzer'] []
bs4.dammit ['bs4_fuzzer'] []
pickle [] []
soupsieve.__meta__ [] []
bs4.builder._lxml [] []
...bs4_fuzzer ['bs4_fuzzer'] []

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
bs4_fuzzer fuzzerLogFile-bs4_fuzzer.data fuzzerLogFile-bs4_fuzzer.data.yaml all_cov.json