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

Table of contents

Project overview: libwebsockets
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: lws_upng_inflate_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/libwebsockets/lws_upng_inflate_fuzzer.cpp
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: 2025-11-16

Project overview: libwebsockets

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
2.0%
18 / 1127
Cyclomatic complexity statically reachable by fuzzers
2.0%
179 / 9416
Runtime code coverage of functions
2.0%
20 / 1127

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
lws_upng_inflate_fuzzer /src/libwebsockets/lws_upng_inflate_fuzzer.cpp 28 1365 7 5 495 200 lws_upng_inflate_fuzzer.cpp

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: lws_upng_inflate_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 11 13.7%
gold [1:9] 1 1.25%
yellow [10:29] 1 1.25%
greenyellow [30:49] 7 8.75%
lawngreen 50+ 60 75.0%
All colors 80 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
3 62 _lws_upng_inflate_data call site: 00062 _lws_log
2 5 _lws_log call site: 00005 lws_strncpy
2 17 lws_upng_inflator_create call site: 00017 _lws_log
1 3 lws_upng_inflator_create call site: 00003 _lws_log
1 12 lws_snprintf call site: 00012 lws_snprintf
1 14 __lws_logv call site: 00014 lws_snprintf
1 78 lws_upng_inflator_destroy call site: 00078 lws_realloc

Runtime coverage analysis

Covered functions
21
Functions that are reachable but not covered
9
Reachable functions
28
Percentage of reachable functions covered
67.86%
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
/src/libwebsockets/lws_upng_inflate_fuzzer.cpp 2
/src/libwebsockets/lib/misc/upng-gzip.c 10
/src/libwebsockets/lib/core/alloc.c 2
/src/libwebsockets/lib/core/logs.c 3
/src/libwebsockets/lib/core/libwebsockets.c 2

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
rops_handle_POLLIN_h1 /src/libwebsockets/lib/roles/h1/ops-h1.c 3 ['N/A', 'N/A', 'N/A'] 34 0 300 48 21 669 0 5191 5146
lws_create_context /src/libwebsockets/lib/core/context.c 1 ['N/A'] 26 0 1963 215 77 547 0 3481 714
lws_display_render_jpeg /src/libwebsockets/lib/misc/dlo/dlo-jpeg.c 1 ['N/A'] 9 0 423 49 20 71 0 475 410
secstream_h2 /src/libwebsockets/lib/secure-streams/protocols/ss-h2.c 5 ['N/A', 'int', 'N/A', 'N/A', 'size_t'] 27 0 210 34 11 384 0 2492 380
lws_cache_heap_write /src/libwebsockets/lib/misc/cache-ttl/heap.c 6 ['N/A', 'N/A', 'N/A', 'size_t', 'size_t', 'N/A'] 16 0 318 39 14 59 0 281 171
rops_perform_user_POLLOUT_h2 /src/libwebsockets/lib/roles/h2/ops-h2.c 1 ['N/A'] 32 0 860 121 48 437 0 3305 166
lws_display_render_png /src/libwebsockets/lib/misc/dlo/dlo-png.c 1 ['N/A'] 8 0 435 49 20 42 0 360 141
lws_context_default_loop_run_destroy /src/libwebsockets/lib/core/libwebsockets.c 1 ['N/A'] 28 0 46 9 4 370 0 2139 122
rops_handle_POLLIN_netlink /src/libwebsockets/lib/roles/netlink/ops-netlink.c 3 ['N/A', 'N/A', 'N/A'] 19 0 1432 160 35 308 0 1835 108
lws_create_adopt_udp /src/libwebsockets/lib/core-net/adopt.c 10 ['N/A', 'N/A', 'int', 'int', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 24 0 206 16 6 490 0 2974 100

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

Functions statically reachable by fuzzers
62.0%
702 / 1127
Cyclomatic complexity statically reachable by fuzzers
76.0%
7199 / 9416

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/libwebsockets/lws_upng_inflate_fuzzer.cpp

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=['_lws_upng_inflate_data', '_lws_log', 'lws_upng_inflator_create', 'lws_snprintf', '__lws_logv', 'lws_upng_inflator_destroy']

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

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
[] []
/src/libwebsockets/lib/core-net/client/connect2.c [] []
/src/libwebsockets/lib/roles/http/server/server.c [] []
/src/libwebsockets/lib/misc/dlo/dlo-text.c [] []
/src/libwebsockets/lib/plat/unix/unix-init.c [] []
/src/libwebsockets/lib/roles/http/client/client-http.c [] []
/src/libwebsockets/lib/misc/lejp.c [] []
/src/libwebsockets/lib/core-net/client/client.c [] []
/src/libwebsockets/lib/core/logs.c ['lws_upng_inflate_fuzzer'] ['lws_upng_inflate_fuzzer']
/src/libwebsockets/lib/roles/listen/ops-listen.c [] []
/src/libwebsockets/lib/event-libs/poll/poll.c [] []
/src/libwebsockets/lib/tls/lws-gencrypto-common.c [] []
/src/libwebsockets/lib/roles/h1/ops-h1.c [] []
/src/libwebsockets/lib/tls/tls-sessions.c [] []
/src/libwebsockets/lib/misc/base64-decode.c [] []
/src/libwebsockets/lib/secure-streams/secure-streams.c [] []
/src/libwebsockets/lib/core/context.c [] []
/src/libwebsockets/lib/roles/raw-file/ops-raw-file.c [] []
/src/libwebsockets/lib/roles/h2/hpack.c [] []
/src/libwebsockets/lib/core-net/client/connect4.c [] []
/src/libwebsockets/lib/core-net/state.c [] []
/usr/lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/limits [] []
/src/libwebsockets/lib/misc/dlo/dlo-jpeg.c [] []
/src/libwebsockets/lib/core-net/sorted-usec-list.c [] []
/src/libwebsockets/lib/roles/h2/http2.c [] []
/src/libwebsockets/lib/secure-streams/protocols/ss-h2.c [] []
/src/libwebsockets/lib/plat/unix/unix-fds.c [] []
/src/libwebsockets/lib/core-net/wsi.c [] []
/src/libwebsockets/lib/system/smd/smd.c [] []
/src/libwebsockets/lib/roles/http/cookie.c [] []
/src/libwebsockets/lib/core-net/wsi-timeout.c [] []
/src/libwebsockets/lib/core/alloc.c ['lws_upng_inflate_fuzzer'] ['lws_upng_inflate_fuzzer']
/src/libwebsockets/lib/core-net/pollfd.c [] []
/src/libwebsockets/lib/core-net/vhost.c [] []
/src/libwebsockets/lib/core-net/service.c [] []
/src/libwebsockets/lib/tls/openssl/openssl-x509.c [] []
/src/libwebsockets/lib/roles/ws/client-parser-ws.c [] []
/src/libwebsockets/lib/tls/openssl/openssl-client.c [] []
/src/libwebsockets/lib/core-net/dummy-callback.c [] []
/src/libwebsockets/lib/core-net/network.c [] []
/src/libwebsockets/lib/roles/h2/ops-h2.c [] []
/src/libwebsockets/lib/misc/dlo/dlo-font-mcufont.c [] []
/src/libwebsockets/lib/roles/ws/ops-ws.c [] []
/src/libwebsockets/lib/roles/http/header.c [] []
/src/libwebsockets/lib/secure-streams/protocols/ss-raw.c [] []
/usr/include/openssl/x509.h [] []
/src/libwebsockets/lib/roles/pipe/ops-pipe.c [] []
/src/libwebsockets/include/libwebsockets/lws-vfs.h [] []
/src/libwebsockets/lib/core/lws_dll2.c [] []
/src/libwebsockets/lib/system/stdin.c [] []
/src/libwebsockets/include/libwebsockets/lws-dll2.h [] []
/src/libwebsockets/lib/core-net/client/conmon.c [] []
/src/libwebsockets/lib/tls/openssl/openssl-tls.c [] []
/src/libwebsockets/lib/secure-streams/system/fetch-policy/fetch-policy.c [] []
/src/libwebsockets/lib/core/buflist.c [] []
/src/libwebsockets/lib/core/vfs.c [] []
/src/libwebsockets/lib/tls/tls-server.c [] []
/src/libwebsockets/lib/plat/unix/unix-misc.c [] []
/src/libwebsockets/lib/core/libwebsockets.c ['lws_upng_inflate_fuzzer'] ['lws_upng_inflate_fuzzer']
/src/libwebsockets/lib/roles/http/date.c [] []
/src/libwebsockets/lib/core-net/client/connect3.c [] []
/src/libwebsockets/lib/misc/lwsac/lwsac.c [] []
/src/libwebsockets/lib/tls/tls-network.c [] []
/src/libwebsockets/lib/secure-streams/policy-json.c [] []
/src/libwebsockets/lib/tls/tls-client.c [] []
/src/libwebsockets/lib/misc/dlo/dlo.c [] []
/src/libwebsockets/lib/misc/upng-gzip.c ['lws_upng_inflate_fuzzer'] ['lws_upng_inflate_fuzzer']
/src/libwebsockets/lib/misc/cache-ttl/heap.c [] []
/src/libwebsockets/lib/misc/upng.c [] []
/src/libwebsockets/lib/plat/unix/unix-sockets.c [] []
/src/libwebsockets/lib/misc/sha-1.c [] []
/src/libwebsockets/lib/roles/netlink/ops-netlink.c [] []
/src/libwebsockets/lib/core-net/route.c [] []
/src/libwebsockets/lws_upng_inflate_fuzzer.cpp ['lws_upng_inflate_fuzzer'] ['lws_upng_inflate_fuzzer']
/src/libwebsockets/lib/core-net/close.c [] []
/src/libwebsockets/lib/core-net/client/sort-dns.c [] []
/src/libwebsockets/lib/plat/unix/unix-caps.c [] []
/src/libwebsockets/lib/core-net/adopt.c [] []
/src/libwebsockets/lib/roles/ws/server-ws.c [] []
/src/libwebsockets/lib/core-net/client/connect.c [] []
/src/libwebsockets/lib/tls/openssl/openssl-ssl.c [] []
/src/libwebsockets/lib/secure-streams/protocols/ss-h1.c [] []
/src/libwebsockets/lib/misc/cache-ttl/file.c [] []
/src/libwebsockets/lib/core-net/output.c [] []
/src/libwebsockets/lib/roles/ws/client-ws.c [] []
/src/libwebsockets/lib/tls/openssl/openssl-server.c [] []
/src/libwebsockets/lib/tls/tls.c [] []
/src/libwebsockets/lib/secure-streams/protocols/ss-ws.c [] []
/src/libwebsockets/lib/roles/raw-skt/ops-raw-skt.c [] []
/src/libwebsockets/include/libwebsockets/lws-write.h [] []
/src/libwebsockets/lib/plat/unix/unix-file.c [] []
/src/libwebsockets/lib/plat/unix/unix-service.c [] []
/src/libwebsockets/lib/tls/openssl/openssl-session.c [] []
/src/libwebsockets/lib/secure-streams/policy-common.c [] []
/src/libwebsockets/lib/tls/openssl/lws-genhash.c [] []
/src/libwebsockets/lib/secure-streams/system/captive-portal-detect/captive-portal-detect.c [] []
/src/libwebsockets/lib/roles/http/parsers.c [] []
/src/libwebsockets/lib/misc/cache-ttl/lws-cache-ttl.c [] []
/src/libwebsockets/lib/plat/unix/unix-pipe.c [] []
/src/libwebsockets/lib/misc/jpeg.c [] []
/src/libwebsockets/lib/misc/dlo/dlo-png.c [] []
/src/libwebsockets/lib/system/system.c [] []

Directories in report

Directory
/usr/lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/
/src/libwebsockets/lib/misc/cache-ttl/
/src/libwebsockets/lib/event-libs/poll/
/src/libwebsockets/lib/secure-streams/system/fetch-policy/
/usr/include/openssl/
/src/libwebsockets/lib/system/
/src/libwebsockets/
/src/libwebsockets/lib/roles/ws/
/src/libwebsockets/lib/core/
/src/libwebsockets/lib/roles/raw-file/
/src/libwebsockets/lib/secure-streams/system/captive-portal-detect/
/src/libwebsockets/lib/roles/h2/
/src/libwebsockets/lib/plat/unix/
/src/libwebsockets/lib/tls/openssl/
/src/libwebsockets/include/libwebsockets/
/src/libwebsockets/lib/tls/
/src/libwebsockets/lib/secure-streams/protocols/
/src/libwebsockets/lib/misc/dlo/
/src/libwebsockets/lib/roles/http/
/src/libwebsockets/lib/misc/
/src/libwebsockets/lib/roles/http/server/
/src/libwebsockets/lib/roles/netlink/
/src/libwebsockets/lib/system/smd/
/src/libwebsockets/lib/roles/pipe/
/src/libwebsockets/lib/core-net/client/
/src/libwebsockets/lib/misc/lwsac/
/src/libwebsockets/lib/secure-streams/
/src/libwebsockets/lib/roles/listen/
/src/libwebsockets/lib/core-net/
/src/libwebsockets/lib/roles/raw-skt/
/src/libwebsockets/lib/roles/h1/
/src/libwebsockets/lib/roles/http/client/

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
lws_upng_inflate_fuzzer fuzzerLogFile-0-paOpPPjSz3.data fuzzerLogFile-0-paOpPPjSz3.data.yaml lws_upng_inflate_fuzzer.covreport