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

Table of contents

Project overview: libxslt
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: xpath
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Fuzzer: xslt
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
libxslt/tests/fuzz/xpath.c
Dictionary
Fuzzer function priority
libxslt/tests/fuzz/xslt.c
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: 2025-10-10

Project overview: libxslt

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
56.0%
1273 / 2268
Cyclomatic complexity statically reachable by fuzzers
68.0%
16925 / 24723
Runtime code coverage of functions
60.0%
1358 / 2268

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
xpath libxslt/tests/fuzz/xpath.c 1058 1292 47 46 34623 13556 xpath.c
xslt libxslt/tests/fuzz/xslt.c 1315 1035 52 49 43513 16999 xslt.c

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: xpath

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 3417 63.8%
gold [1:9] 164 3.06%
yellow [10:29] 89 1.66%
greenyellow [30:49] 84 1.56%
lawngreen 50+ 1599 29.8%
All colors 5353 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
341 3218 xsltCreateRVT call site: 03218 xsltApplyOneTemplate
175 3658 xmlNewCDataBlock call site: 03658 xsltApplySequenceConstructor
124 1802 xmlBuildURI call site: 01802 xmlCatalogXMLResolve
110 4175 xmlCreateIntSubset call site: 04175 xmlXIncludeRecurseDoc
105 4065 xsltLoadDocument call site: 04065 xmlXIncludeProcessFlags
94 4402 xmlXPtrEval call site: 04402 xmlXIncludeCopyXPointer
93 5070 xsltRegisterAllElement call site: 05070 xsltNumberFormat
80 4510 xsltRegisterAllFunctions call site: 04510 xsltKeyFunction
77 4862 xmlXPathEval call site: 04862 xsltDefaultProcessOneNode
61 1497 xmlHashUpdateInternal call site: 01497 xmlCopyEntitiesTable
61 3560 xsltFreeDocumentKeys call site: 03560 xsltApplySequenceConstructor
52 3852 xmlXPathCastNumberToString call site: 03852 xsltEvalAttrValueTemplate

Runtime coverage analysis

Covered functions
755
Functions that are reachable but not covered
439
Reachable functions
1058
Percentage of reachable functions covered
58.51%
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
libxslt/tests/fuzz/xpath.c 1
libxslt/tests/fuzz/fuzz.c 7
libxml2/hash.c 30
libxml2/threads.c 10
libxml2/dict.c 22
libxml2/error.c 15
libxml2/xmlmemory.c 1
libxml2/globals.c 21
libxml2/encoding.c 16
libxml2/xpath.c 170
libxml2/xmlIO.c 18
libxml2/catalog.c 33
libxml2/parser.c 134
libxml2/parserInternals.c 42
libxml2/SAX2.c 6
libxml2/buf.c 26
libxml2/HTMLparser.c 2
libxml2/xmlstring.c 22
libxml2/tree.c 97
libxml2/./include/private/memory.h 1
libxml2/chvalid.c 1
libxml2/uri.c 40
libxml2/entities.c 15
libxml2/valid.c 41
libxml2/list.c 3
libxslt/libxslt/transform.c 48
libxslt/libxslt/extensions.c 15
libxslt/libxslt/xsltutils.c 11
libxslt/libxslt/variables.c 23
libxml2/./timsort.h 12
libxslt/libxslt/extra.c 1
libxml2/debugXML.c 27
libxslt/libxslt/templates.c 6
libxslt/libxslt/keys.c 9
libxslt/libxslt/namespaces.c 3
libxslt/libxslt/imports.c 4
libxslt/libxslt/attributes.c 2
libxslt/libxslt/attrvt.c 1
libxslt/libxslt/functions.c 12
libxslt/libxslt/documents.c 4
libxslt/libxslt/security.c 4
libxml2/xinclude.c 27
libxml2/xpointer.c 8
libxslt/libxslt/xslt.c 2
libxslt/libxslt/numbers.c 16
libxslt/libxslt/pattern.c 9

Fuzzer: xslt

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 2312 31.8%
gold [1:9] 231 3.18%
yellow [10:29] 49 0.67%
greenyellow [30:49] 27 0.37%
lawngreen 50+ 4631 63.8%
All colors 7250 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
316 2454 xsltRegisterAllExtras call site: 02454 xmlXPathDebugDumpObject
193 5897 xsltLoadDocument call site: 05897 xmlXIncludeProcessFlags
122 1809 xmlBuildURI call site: 01809 xmlCatalogXMLResolve
116 4599 xmlNodeDumpOutputInternal call site: 04599 xhtmlNodeDumpOutput
75 6220 xmlXPtrEval call site: 06220 xmlXIncludeCopyXPointer
69 4352 xmlNodeDumpOutput call site: 04352 xhtmlNodeDumpOutput
68 4423 xmlHashScan call site: 04423 xmlNodeDumpOutputInternal
49 1501 xmlNewDtd call site: 01501 xmlCopyEntitiesTable
48 6422 xsltRegisterAllFunctions call site: 06422 xmlXPathNumberFunction
31 683 xmlRMutexUnlock call site: 00683 xmlParseXMLCatalogFile
30 4725 xmlOutputBufferClose call site: 04725 xsltSaveResultToFilename
27 7156 xsltApplyStylesheetInternal call site: 07156 xsltEvalUserParams

Runtime coverage analysis

Covered functions
1344
Functions that are reachable but not covered
269
Reachable functions
1315
Percentage of reachable functions covered
79.54%
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
libxslt/tests/fuzz/xslt.c 1
libxslt/tests/fuzz/fuzz.c 11
libxml2/hash.c 32
libxml2/threads.c 10
libxml2/dict.c 23
libxml2/error.c 15
libxml2/xmlmemory.c 1
libxml2/globals.c 25
libxml2/encoding.c 20
libxml2/xpath.c 168
libxml2/xmlIO.c 29
libxml2/catalog.c 33
libxml2/xmlstring.c 23
libxml2/parser.c 134
libxml2/parserInternals.c 42
libxml2/SAX2.c 6
libxml2/buf.c 26
libxml2/HTMLparser.c 6
libxml2/tree.c 105
libxml2/./include/private/memory.h 1
libxml2/chvalid.c 1
libxml2/uri.c 40
libxml2/entities.c 17
libxml2/valid.c 41
libxml2/list.c 3
libxslt/libxslt/xslt.c 35
libxslt/libxslt/xsltutils.c 21
libxslt/libxslt/extra.c 3
libxslt/libxslt/extensions.c 36
libxml2/debugXML.c 27
libxslt/libxslt/preproc.c 29
libxslt/libxslt/templates.c 8
libxslt/libxslt/transform.c 54
libxml2/./timsort.h 12
libxslt/libxslt/security.c 7
libxslt/libxslt/imports.c 8
libxslt/libxslt/variables.c 31
libxslt/libxslt/keys.c 16
libxslt/libxslt/namespaces.c 5
libxslt/libxslt/attributes.c 20
libxslt/libxslt/attrvt.c 6
libxml2/HTMLtree.c 8
libxml2/xmlsave.c 32
libxslt/libxslt/pattern.c 30
libxslt/libxslt/documents.c 7
libxslt/libxslt/functions.c 12
libxml2/xinclude.c 27
libxml2/xpointer.c 8
libxslt/libxslt/numbers.c 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
LLVMFuzzerInitialize /src/libxslt/tests/fuzz/xpath.c 2 ['N/A', 'N/A'] 32 0 16 3 2 1053 0 11656 1987
xmlParseInNodeContext /src/libxml2/parser.c 5 ['N/A', 'N/A', 'int', 'int', 'N/A'] 57 0 161 28 12 612 0 7820 725
xmlParseSGMLCatalog /src/libxml2/catalog.c 4 ['N/A', 'N/A', 'N/A', 'int'] 14 0 1091 234 79 123 6 1566 255
xmlDOMWrapAdoptNode /src/libxml2/tree.c 6 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'int'] 12 0 249 51 15 50 0 581 247
xmlSAX2StartElementNs /src/libxml2/SAX2.c 9 ['N/A', 'N/A', 'N/A', 'N/A', 'int', 'N/A', 'int', 'int', 'N/A'] 28 0 838 126 50 195 0 1601 198
xmlValidateNMToken /src/libxml2/tree.c 2 ['N/A', 'int'] 2 0 1177 272 110 3 0 146 110
xmlDOMWrapCloneNode /src/libxml2/tree.c 8 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'int', 'int'] 13 0 1572 297 98 108 0 807 98

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

Functions statically reachable by fuzzers
70.0%
1586 / 2268
Cyclomatic complexity statically reachable by fuzzers
83.0%
20420 / 24723

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.

libxslt/tests/fuzz/xpath.c

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=['xsltCreateRVT', 'xmlNewCDataBlock', 'xmlBuildURI', 'xmlCreateIntSubset', 'xsltLoadDocument', 'xmlXPtrEval', 'xsltRegisterAllElement', 'xsltRegisterAllFunctions', 'xmlXPathEval', 'xmlHashUpdateInternal']

libxslt/tests/fuzz/xslt.c

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=['xsltRegisterAllExtras', 'xsltLoadDocument', 'xmlBuildURI', 'xmlNodeDumpOutputInternal', 'xmlXPtrEval', 'xmlNodeDumpOutput', 'xmlHashScan', 'xmlNewDtd', 'xsltRegisterAllFunctions', 'xmlRMutexUnlock']

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
xmlFormatError 188 98 52.12% ['xslt', 'xpath']
xmlErrString 321 159 49.53% ['xslt', 'xpath']
xmlNodeSetDoc 69 15 21.73% ['xslt', 'xpath']
xmlInsertNode 63 32 50.79% ['xslt', 'xpath']
xmlFreeAttribute 32 17 53.12% ['xslt', 'xpath']
xmlXPathCacheObjectCopy 31 17 54.83% ['xslt', 'xpath']
xsltLoadDocument 39 15 38.46% ['xslt', 'xpath']
xmlLoadResource 41 15 36.58% ['xslt', 'xpath']
xmlStaticCopyNodeList 62 23 37.09% ['xslt', 'xpath']
xmlNodeAddContentLen 31 11 35.48% ['xslt', 'xpath']
xmlNodeSetContentInternal 32 15 46.87% ['xslt']
xmlOutputBufferWrite 63 32 50.79% ['xslt']
xsltCheckWritePath 39 13 33.33% ['xslt']
xsltDocumentElem 396 61 15.40% ['xslt']
xsltCallTemplate 55 26 47.27% ['xslt', 'xpath']
xsltGatherNamespaces 58 7 12.06% ['xslt']

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/libxslt/libxslt/transform.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/xsltlocale.c [] []
/src/libxml2/xmlsave.c ['xslt'] ['xslt']
/src/libxslt/libexslt/crypto.c [] []
/src/libxslt/libxslt/variables.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/globals.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/tree.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/namespaces.c ['xpath', 'xslt'] ['xslt']
/src/libxml2/hash.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/valid.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libexslt/common.c [] []
/src/libxml2/encoding.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/extra.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/./include/private/memory.h ['xpath', 'xslt'] []
/src/libxslt/libexslt/dynamic.c [] []
/src/libxslt/libxslt/attrvt.c ['xpath', 'xslt'] ['xslt']
/src/libxml2/xmlstring.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/./timsort.h ['xpath', 'xslt'] []
/src/libxslt/libxslt/attributes.c ['xpath', 'xslt'] ['xslt']
/src/libxslt/libxslt/security.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/threads.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/preproc.c ['xslt'] ['xslt']
/src/libxslt/libxslt/imports.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libexslt/sets.c [] []
/src/libxslt/libexslt/functions.c [] []
/src/libxml2/uri.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libexslt/exslt.c [] []
/src/libxml2/SAX2.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/parser.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/dict.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/xmlmemory.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/xpath.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/xpointer.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/chvalid.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/HTMLparser.c ['xpath', 'xslt'] ['xslt']
/src/libxml2/catalog.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libexslt/math.c [] []
/src/libxslt/libxslt/xsltutils.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/debugXML.c ['xpath', 'xslt'] []
/src/libxml2/parserInternals.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/HTMLtree.c ['xslt'] ['xslt']
/src/libxml2/entities.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/list.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/xslt.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libexslt/strings.c [] []
/src/libxslt/libexslt/saxon.c [] []
/src/libxslt/libxslt/extensions.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/documents.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/error.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libxslt/keys.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxml2/xinclude.c ['xpath', 'xslt'] []
/src/libxslt/libxslt/pattern.c ['xpath', 'xslt'] ['xslt']
/src/libxml2/buf.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/tests/fuzz/fuzz.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/libexslt/date.c [] []
/src/libxslt/libxslt/functions.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/tests/fuzz/xslt.c ['xslt'] ['xslt']
/src/libxslt/libxslt/numbers.c ['xpath', 'xslt'] ['xslt']
/src/libxml2/xmlIO.c ['xpath', 'xslt'] ['xpath', 'xslt']
/src/libxslt/tests/fuzz/xpath.c ['xpath'] ['xpath']
/src/libxslt/libxslt/templates.c ['xpath', 'xslt'] ['xslt']

Directories in report

Directory
/src/libxslt/libxslt/
/src/libxslt/libexslt/
/src/libxml2/
/src/libxslt/tests/fuzz/
/src/libxml2/./include/private/
/src/libxml2/./

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
xpath fuzzerLogFile-0-Mb8LEpT0kn.data fuzzerLogFile-0-Mb8LEpT0kn.data.yaml xpath.covreport
xslt fuzzerLogFile-0-RP46nhEdQ5.data fuzzerLogFile-0-RP46nhEdQ5.data.yaml xslt.covreport