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

Table of contents

Project overview: python-pypdf
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_encryption
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_encryption.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: 2026-02-16

Project overview: python-pypdf

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
21.0%
178 / 834
Cyclomatic complexity statically reachable by fuzzers
22.0%
693 / 3094
Runtime code coverage of functions
24.0%
202 / 834

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
fuzz_encryption /src/fuzz_encryption.py 401 1172 15 15 423 1359 fuzz_encryption.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_encryption

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 1176 63.5%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 674 36.4%
All colors 1850 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
248 1311 pypdf._writer.PdfWriter.write_stream call site: 01311 pypdf._writer.PdfWriter.write
159 1108 pypdf._writer.PdfWriter.__init__ call site: 01108 pypdf._writer.PdfWriter.clone_document_from_reader
89 836 pypdf._reader.PdfReader._read_xref call site: 00836 pypdf._reader.PdfReader._read_pdf15_xref_stream
62 395 pypdf._crypt_providers._fallback.CryptRC4.encrypt call site: 00395 pypdf._reader.PdfReader.read
61 970 pypdf._encryption.Encryption.verify call site: 00970 pypdf._encryption.AlgV4.verify_owner_password
59 460 pypdf._reader.PdfReader.cache_indirect_object call site: 00460 pypdf._reader.PdfReader.read
56 594 pypdf.generic._data_structures.ArrayObject.read_from_stream call site: 00594 pypdf.generic._base.BooleanObject.read_from_stream
52 715 pypdf._reader.PdfReader._read_standard_xref_table call site: 00715 pypdf._reader.PdfReader._rebuild_xref_table
27 233 pypdf.generic._data_structures.DictionaryObject.read_from_stream call site: 00233 pypdf._reader.PdfReader.read
24 787 pypdf._reader.PdfReader._read_standard_xref_table call site: 00787 pypdf._reader.PdfReader.read
14 280 pypdf.generic._base.NumberObject.read_from_stream call site: 00280 pypdf._utils.read_non_whitespace
14 336 pypdf._reader.PdfReader.read_object_header call site: 00336 pypdf._reader.PdfReader.read

Runtime coverage analysis

Covered functions
262
Functions that are reachable but not covered
307
Reachable functions
401
Percentage of reachable functions covered
23.44%
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.
Function name source code lines source lines hit percentage hit

Files reached

filename functions hit
/ 1
...fuzz_encryption 9
pypdf._writer 114
pypdf._reader 88
pypdf._utils 20
pypdf.generic._data_structures 86
pypdf.generic._base 37
pypdf._encryption 88
pypdf._crypt_providers._cryptography 17
pypdf._crypt_providers._fallback 7
pypdf._crypt_providers._pycryptodome 7
pypdf.generic._utils 26
pypdf._doc_common 12
pypdf._page 9
pypdf.filters 65

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
pypdf._writer.PdfWriter.update_page_form_field_values pypdf._writer 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 45 0 6 23 12 317 1 1114 307
pypdf._writer.PdfWriter.append pypdf._writer 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 45 0 3 4 5 297 0 1050 250
pypdf._page.VirtualListImages.__getitem__ pypdf._page 2 ['N/A', 'N/A'] 46 0 0 5 5 296 0 1041 232
pypdf.xmp.XmpInformation.dc_date pypdf.xmp 2 ['N/A', 'N/A'] 4 0 4 2 4 50 0 159 144
pypdf._text_extraction._layout_mode._fixed_width_page.text_show_operations pypdf._text_extraction._layout_mode._fixed_width_page 4 ['N/A', 'N/A', 'N/A', 'N/A'] 4 0 10 6 5 49 0 163 112
pypdf._page.PageObject._merge_page pypdf._page 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 45 0 12 9 7 275 5 957 90
pypdf.generic._data_structures.ContentStream._parse_content_stream pypdf.generic._data_structures 2 ['N/A', 'N/A'] 39 0 5 4 5 184 1 659 77
pypdf._doc_common.PdfDocCommon.get_form_text_fields pypdf._doc_common 2 ['N/A', 'N/A'] 7 0 1 3 4 37 0 125 76
pypdf._page.PageObject.extract_text pypdf._page 9 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 45 0 2 13 8 300 0 1053 72
pypdf._writer.PdfWriter.remove_text pypdf._writer 2 ['N/A', 'N/A'] 44 0 3 4 5 263 0 922 57

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

Functions statically reachable by fuzzers
40.0%
332 / 834
Cyclomatic complexity statically reachable by fuzzers
46.0%
1410 / 3094

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_encryption.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=['pypdf._writer.PdfWriter.write_stream', 'pypdf._writer.PdfWriter.__init__', 'pypdf._reader.PdfReader._read_xref', 'pypdf._crypt_providers._fallback.CryptRC4.encrypt', 'pypdf._encryption.Encryption.verify', 'pypdf._reader.PdfReader.cache_indirect_object', 'pypdf.generic._data_structures.ArrayObject.read_from_stream', 'pypdf._reader.PdfReader._read_standard_xref_table', 'pypdf.generic._data_structures.DictionaryObject.read_from_stream']

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
pypdf._writer.PdfWriter.__init__._get_clone_from 37 17 45.94% ['fuzz_encryption']
pypdf._writer.PdfWriter._add_page 33 0 0.0% []
pypdf._writer.PdfWriter.update_page_form_field_values 64 0 0.0% []
pypdf._writer.PdfWriter._write_increment 34 0 0.0% ['fuzz_encryption']
pypdf._writer.PdfWriter.compress_identical_objects.replace_in_obj 40 0 0.0% []
pypdf._writer.PdfWriter._remove_objects_from_page__clean_forms 34 0 0.0% []
pypdf._writer.PdfWriter.merge 62 0 0.0% []
pypdf._writer.PdfWriter._insert_filtered_annotations 36 0 0.0% []
pypdf._reader.PdfReader.get_object 75 22 29.33% ['fuzz_encryption']
pypdf._reader.PdfReader.read 41 19 46.34% ['fuzz_encryption']
pypdf._reader.PdfReader._rebuild_xref_table 37 0 0.0% ['fuzz_encryption']
pypdf.generic._appearance_stream.TextStreamAppearance._scale_text 36 0 0.0% []
pypdf.generic._appearance_stream.TextStreamAppearance._generate_appearance_stream_data 60 0 0.0% []
pypdf.generic._appearance_stream.TextStreamAppearance.from_text_annotation 51 0 0.0% []
pypdf.generic._data_structures.DictionaryObject._clone 50 0 0.0% []
pypdf.generic._data_structures.DictionaryObject.read_from_stream 93 30 32.25% ['fuzz_encryption']
pypdf.generic._data_structures.TreeObject.insert_child 38 0 0.0% []
pypdf.generic._data_structures.ContentStream._read_inline_image 51 0 0.0% []
pypdf.generic._data_structures.Destination.__init__ 32 0 0.0% []
pypdf.generic._image_inline.extract_inline_default 32 0 0.0% []
pypdf._doc_common.PdfDocCommon._get_named_destinations 46 0 0.0% []
pypdf._doc_common.PdfDocCommon.get_pages_showing_field._get_inherited 39 2 5.128% ['fuzz_encryption']
pypdf._doc_common.PdfDocCommon._get_outline 33 0 0.0% []
pypdf._doc_common.PdfDocCommon._build_outline_item 46 0 0.0% []
pypdf._doc_common.PdfDocCommon._flatten 39 0 0.0% ['fuzz_encryption']
pypdf._page.PageObject._merge_resources.compute_unique_key 33 0 0.0% []
pypdf._page.PageObject.replace_contents 34 0 0.0% []
pypdf._page.PageObject._merge_page 46 0 0.0% []
pypdf._page.PageObject._merge_page_writer 70 0 0.0% []
pypdf._page.PageObject._extract_text 79 0 0.0% []
pypdf._page._VirtualList.__delitem__ 36 0 0.0% []
pypdf._cmap._parse_encoding 40 0 0.0% []
pypdf._cmap.parse_bfrange 35 0 0.0% []
pypdf._font.Font.from_font_resource 43 0 0.0% []
pypdf._text_extraction._layout_mode._fixed_width_page.recurs_to_target_op 84 0 0.0% []
pypdf._text_extraction.crlf_space_check 37 0 0.0% []
pypdf.generic._utils.read_string_from_stream 43 0 0.0% ['fuzz_encryption']
Crypto.Cipher.ARC4.ARC4Cipher 36 10 27.77% ['fuzz_encryption']
Crypto.Util.Padding.pad 36 8 22.22% ['fuzz_encryption']

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
[] []
warnings [] []
pypdf._text_extraction._layout_mode._text_state_manager [] []
pypdf.generic._base ['fuzz_encryption'] []
xml [] []
decimal [] []
struct [] []
pypdf.generic [] []
json [] []
pypdf.xmp [] []
get_text_operands [] []
binascii [] []
subprocess [] []
bisect [] []
pypdf.generic._utils ['fuzz_encryption'] []
pypdf._text_extraction._layout_mode._fixed_width_page [] []
pypdf._codecs.core_font_metrics [] []
pypdf._codecs.symbol [] []
pypdf._text_extraction [] []
crlf_space_check [] []
pypdf._crypt_providers [] []
pypdf._crypt_providers._cryptography ['fuzz_encryption'] []
pypdf._codecs._codecs [] []
pypdf._doc_common ['fuzz_encryption'] []
pypdf._codecs.zapfding [] []
cryptography [] []
pypdf._crypt_providers._fallback ['fuzz_encryption'] []
pypdf.pagerange [] []
pypdf._xobj_image_helpers [] []
[] []
logging [] []
pypdf.generic._image_inline [] []
typing [] []
pypdf.constants [] []
pypdf._codecs.std [] []
math [] []
get_display_str [] []
pypdf._codecs [] []
pypdf [] []
base64 [] []
collections [] []
pypdf._crypt_providers._base [] []
pypdf.generic._appearance_stream [] []
pypdf.generic._fit [] []
pypdf._reader ['fuzz_encryption'] []
pathlib [] []
atheris [] []
pypdf._font [] []
itertools [] []
datetime [] []
pypdf._page ['fuzz_encryption'] []
pypdf.generic._outline [] []
pypdf._text_extraction._layout_mode [] []
pypdf._cmap [] []
pypdf._text_extraction._layout_mode._text_state_params [] []
secrets [] []
pypdf._protocols [] []
pypdf.annotations [] []
pypdf._version [] []
pypdf._encryption ['fuzz_encryption'] []
copy [] []
io [] []
pypdf.generic._viewerpref [] []
shutil [] []
pypdf.errors [] []
pypdf.annotations._markup_annotations [] []
os [] []
zlib [] []
PIL [] []
pypdf.papersizes [] []
...fuzz_encryption ['fuzz_encryption'] []
pypdf._crypt_providers._pycryptodome ['fuzz_encryption'] []
_codecs [] []
pypdf.generic._data_structures ['fuzz_encryption'] []
pypdf.types [] []
Crypto [] []
pypdf._writer ['fuzz_encryption'] []
mult [] []
pypdf.generic._files [] []
pypdf._text_extraction._text_extractor [] []
hashlib [] []
tempfile [] []
pypdf.annotations._base [] []
pypdf._page_labels [] []
pypdf.annotations._non_markup_annotations [] []
pypdf._utils ['fuzz_encryption'] []
re [] []
pypdf.filters ['fuzz_encryption'] []
dataclasses [] []
pypdf._codecs.adobe_glyphs [] []
pypdf.generic._link [] []
pypdf.generic._rectangle [] []
pypdf._codecs.pdfdoc [] []
enum [] []
uuid [] []

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_encryption fuzzerLogFile-fuzz_encryption.data fuzzerLogFile-fuzz_encryption.data.yaml all_cov.json