Snyk for C/C++

You can use Snyk to scan C/C++ projects through the CLI. For more information see Getting started with the CLI.

Features of Snyk for C/C++

Feature availability Some features may not be available, depending on your plan. See pricing plans for more details.
Package managers / Features
CLI support
Git support
License scanning
Fix PRs

How Snyk for C/C++ works

Scans are powered by an open-source database, periodically updated with the latest source code from online sources.
To navigate through the vulnerabilities for C/C++, use the Snyk Vuln DB.
When you run the snyk test --unmanaged command, Snyk does the following:
  1. 1.
    Converts all files from your current folder into a list of hashes.
  2. 2.
    Sends the hashes to Snyk scan server.
  3. 3.
    Queries the database to find a list of potentially matching dependencies.
  4. 4.
    Links the dependencies to the known vulnerabilities.
  5. 5.
    Displays the results.
For Snyk to scan the project, the dependencies must be available as source code in the scanned directory. If the dependencies are in a different location, that location must be scanned.

Scanning archives

By default, archives are not scanned. However, Snyk CLI can recursively extract archives to analyze the source code inside.
To enable archive extraction, specify the depth of the extraction using the --max-depth option.
The supported archive formats are:
  • zip-like archives
  • tar archives
  • tar with gzip compression algorithm

Constraints and limitations

The following constraints and limitations are by design. While Snyk may work on improvements in the future, they are not considered an issue. Issues that are planned to be addressed are in the Known issues section.

Source code dependencies need to be available in the scanned folder

For Snyk CLI to be able to find dependencies in your source code, enough of the full dependencies source code needs to be present in the scanned folder.
Having a large percentage of files in their original (unchanged) form is critical to accurately identifying dependencies and reporting the correct set of vulnerabilities back. Modifying that source code reduces the confidence of the scanning engine, resulting in less accurate results. Other potential issues could include dependencies not being identified or being identified incorrectly, as a different version or even a different package.
The example that follows shows a typical package with dependencies listed:
├── deps
│ ├── curl-7.58.0
│ │ ├── include
│ │ │ ├──
│ │ │ ├──
│ │ │ ├── README
│ │ │ └── curl
│ │ ├── install-sh
│ │ ├── lib
│ │ │ ├── asyn.h
│ │ │ ├── base64.c
│ │ │ ├──
│ │ │ ├── config-amigaos.h
│ │ │ ├── conncache.c
│ │ │ ├── conncache.h
│ │ ├── src
│ │ │ ├── tool_binmode.c
│ │ │ ├── tool_binmode.h
│ │ │ ├── tool_bname.c
│ │ │ ├── tool_xattr.c

Data collection note

When you scan C++ projects, the following data is collected and may be stored for troubleshooting purposes:
Hashes of the scanned files: All files are converted to a list of irreversible hashes.
Relative paths to scanned files: The paths to files relative to the directory being scanned are included for better identification and matching. Example: ./project-name/vendor/bzip2-1.0.6/blocksort.c

Snyk CLI for C/C++ projects

Install the Snyk CLI

C/C++ scanning is available in Snyk CLI. See Install the CLI for details.
The minimum version of Snyk CLI with C/C++ scanning is 1.857.0.

Run the test

To test your project for vulnerabilities, run:
$ snyk test --unmanaged
If you scan a Linux project on Windows, make sure the repository is cloned with Linux line endings. See the Known issues section for details.

Displaying dependencies

To display dependencies, use the --print-deps option:
$ snyk test --unmanaged --print-deps
cpython|[email protected]
confidence: 1.000
zip|[email protected]
confidence: 0.993
To learn what files contributed to each dependency being identified, use the --print-dep-paths option:
$ snyk test --unmanaged --print-dep-paths
curl|[email protected]
confidence: 1.000
matching files:
- c-example/deps/curl-7.58.0/CHANGES
- c-example/deps/curl-7.58.0/CMake/
- c-example/deps/curl-7.58.0/CMake/CurlSymbolHiding.cmake
... and 2857 more files

Understanding the confidence level

You may need to change the source code of the dependencies that you use in your software. As Snyk uses file signatures to find the closest possible match to an open-source library, your changes may decrease the accuracy of the identification of the actual library.
To learn how confident Snyk is about the identified dependency and its version, use the --print-deps or --print-dep-paths command line option:
curl|[email protected]
confidence: 0.993
This confidence level shows how confident Snyk is about the actual identification of the dependency. The number can be between 0 and 1 and the higher it is, the more accurate the identification is. Thus a confidence of 1 means that all the files in the source tree fully matched all the expected files in the Snyk database.

JSON output

To get a machine-readable output in JSON, use the --json option:
$ snyk test --unmanaged --json
"issues": [
"pkgName": "curl|",
"pkgVersion": "7.58.0",
"issueId": "CVE-2019-5481",
"fixInfo": {
"isPatchable": false,
"isPinnable": false
"issuesData": {
"CVE-2019-5481": {
"severity": "high",
"CVSSv3": "",
"originalSeverity": "high",
"severityWithCritical": "high",
"type": "vuln",
"alternativeIds": [
"creationTime": "2019-09-16T19:15:00.000Z",
"disclosureTime": "2019-09-16T19:15:00.000Z",
"modificationTime": "2020-10-20T22:15:00.000Z",
"publicationTime": "2019-09-16T19:15:00.000Z",
"credit": [
"id": "CVE-2019-5481",
"packageManager": "cpp",
"packageName": "curl|",
"language": "cpp",
"fixedIn": [
"patches": [],
"exploit": "No Data",
"functions": [
"semver": {
"vulnerable": [
"vulnerableHashes": [
"vulnerableByDistro": {}
"references": [
"title": "",
"url": ""
"internal": {},
"identifiers": {
"CVE": [
"CWE": [],
"title": "CVE-2019-5481",
"description": "",
"license": "",
"proprietary": true,
"nearestFixedInVersion": ""
"fileSignaturesDetails": {
"curl|[email protected]": {
"filePaths": [
"confidence": 1

Command line options

The following snyk command line options are supported with the snyk test --unmanaged and snyk monitor --unmanaged commands:
--org=<ORG_ID> --json --json-file-output=<OUTPUT_FILE_PATH> (snyk test only) --remote-repo-url=<URL> --severity-threshold=<low|medium|high|critical> (snyk test only) --max-depth --print-dep-paths --target-reference=<TARGET_REFERENCE> (snyk monitor only) --project-name=<c-project> (snyk monitor only)
For more information about command line options see the Snyk help docs: Options for scanning with snyk test --unmanaged or snyk monitor --unmanaged.

Import scan results in the Snyk Web UI

To import the test results (issues and dependencies) in the Snyk Web UI, run the snyk monitor --unmanaged command:
$ snyk monitor --unmanaged
Monitoring /c-example (c-example)...
Explore this snapshot at
Notifications about newly disclosed issues related to these dependencies will be emailed to you.
This creates a snapshot of dependencies and vulnerabilities and imports them into the Snyk Web UI, where you can review the issues and see them included in your reports.
Importing a project with unmanaged dependencies creates a new project:
Project with unmanaged dependencies
Project with unmanaged dependencies

Frequently asked questions, Snyk for C/C++

Is my source code sent to Snyk servers?

No. The files are converted to a list of hashes before they are sent for scanning.

Why did Snyk not find any dependencies?

Snyk stores the official releases of many of open-source components in the Snyk database but it is possible that the source code you scanned is not there or is not found. If your scan does not find any dependencies submit a request to support.
Here are a few things that you can check on your own:
  • The source code of the dependencies you scanned is available as source code (unpacked) in the folder that you scanned. If you use a package manager, such as Conan, the source code is likely to be in the Conan cache, along with the source code of other dependencies of your other projects. To scan dependencies managed by a package manager, Snyk recommends that you do that in a clean environment (for example during a build).
  • The source code of the dependencies is not from an official release of the open-source software (OSS) component, and Snyk does not have it in the database
  • The source code of the OSS has been modified too much, so Snyk cannot detect it. If there are too few files and you modify most of them, Snyk cannot match them to a component from the Snyk database. Examples of common modifications are whitespace formatting and adding license or copyright headers.
  • You are on Windows, and Git converted line endings to Windows line endings. Currently Snyk can recognize files that have retained their original line endings.
  • The source code of the OSS components is too new. The Snyk database is refreshed monthly but it takes time for the latest releases to get processed.