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syzkaller is an open-source kernel fuzzer developed by Google that automatically generates and executes test cases to find bugs in operating system kernels. It supports Linux, FreeBSD, Windows, OpenBSD, NetBSD, Fuchsia, and gVisor, and has discovered numerous real vulnerabilities across multiple platforms.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | google/syzkaller |
| Owner | |
| Primary language | Go |
| License | Apache-2.0 — OSI-approved |
| Stars | 6.3k |
| Forks | 1.4k |
| Open issues | 605 |
| Latest release | Unknown |
| Last updated | 2026-07-08 |
| Source | https://github.com/google/syzkaller |
What syzkaller is
syzkaller is a coverage-guided, unsupervised fuzzer written in Go that instruments kernel code to track execution paths and generate syscall sequences targeting uncovered areas. It uses feedback-driven test case generation to maximize code coverage and expose kernel bugs, with support for multiple OS targets through OS-specific harnesses.
Get the syzkaller source
Clone the repository and explore it locally.
git clone https://github.com/google/syzkaller.gitcd syzkaller# follow the project's README for install & configurationNeed it deployed, integrated, or customized instead? DEV.co ships production installs.
Best use cases
Implementation considerations
- Requires Go toolchain and kernel build environment (gcc, clang, kernel headers) for target OS; build and execution time can be substantial for full kernel fuzzing.
- Effective use demands understanding of kernel syscall semantics and OS-specific setup (KASAN/MSAN instrumentation, VM or hardware environment). Refer to OS-specific docs (Linux, FreeBSD, Windows, etc.) for configuration details.
- No official release versioning (latestRelease: n/a); track main branch or specific commits. Verify compatibility between syzkaller version and target kernel version before deployment.
- Generated test cases and crash logs are verbose; requires automated triage and deduplication to manage large fuzzing campaigns. Integration with bug tracking or CI/CD pipelines is recommended.
- Multi-target setup (Linux + FreeBSD + Windows) requires separate harness and VM/hardware infrastructure per OS; plan resource allocation and automation accordingly.
When to avoid it — and what to weigh
- User-Space Application Testing Only — syzkaller is kernel-focused; if your primary need is fuzzing user-space applications or libraries, lighter-weight fuzzers (libFuzzer, AFL) may be more appropriate and easier to integrate.
- No Kernel Source Code Access — syzkaller requires kernel source and instrumentation capabilities. If you cannot modify or instrument the target kernel, effectiveness is severely limited.
- Real-Time Correctness Verification — syzkaller finds bugs through fuzzing but does not formally verify kernel properties or prove absence of bugs. For critical systems requiring formal verification, supplementary proof methods are necessary.
- Minimal Infrastructure or Expertise — Setting up syzkaller for a new OS target or kernel version demands significant systems knowledge, custom harness development, and distributed infrastructure. Not suitable for teams lacking kernel development expertise.
License & commercial use
Apache License 2.0 (Apache-2.0), a permissive OSI-approved license permitting commercial use, modification, and distribution with appropriate attribution and liability disclaimer.
Apache-2.0 permits commercial use. However, this is not an official Google product (per README disclaimer). Ensure your organization's legal team reviews the license terms. No commercial support, SLA, or warranty from Google; community support via mailing list only.
DEV.co evaluation signals
Editorial assessment — not user reviews. Directional, with an explicit confidence level.
| Signal | Assessment |
|---|---|
| Maintenance | Active |
| Documentation | Strong |
| License clarity | Clear |
| Deployment complexity | High |
| DEV.co fit | Good |
| Assessment confidence | High |
syzkaller is designed to find kernel bugs; it does not secure the kernel itself. Fuzzing campaigns generate many test cases and may trigger crashes; isolate fuzzing infrastructure from production. Discovered bugs must be responsibly disclosed per kernel vendor policy. The fuzzer's own security posture (Go runtime, dependency security) should be assessed separately.
Alternatives to consider
AFL (American Fuzzy Lop)
Widely-used, lighter-weight fuzzer for user-space binaries and libraries; simpler setup but less specialized for kernel fuzzing and multi-OS coverage guidance.
libFuzzer
In-process fuzzer for libraries and user-space code; excellent for targeted fuzzing but not designed for kernel-level syscall generation and OS-wide coverage tracking.
Custom kernel testing frameworks (Trinity, LTP)
Linux-specific, manual or semi-automated syscall testing; lower barrier to entry but lack coverage-guided feedback and require explicit test case authoring versus unsupervised generation.
Build on syzkaller with DEV.co software developers
syzkaller enables automated, coverage-guided kernel testing. Assess your infrastructure, kernel expertise, and OS target before starting. Review setup.md and join the mailing list for guidance. Consider Devco for help integrating fuzzing into your CI/CD and security workflows.
Talk to DEV.coRelated on DEV.co
Explore the category and the services that help you build with it.
syzkaller FAQ
Can I use syzkaller on Windows or macOS kernels?
Does syzkaller require source code changes to my kernel?
What infrastructure do I need to run syzkaller?
Is there official support or SLA?
Custom software development services
Open-source adoption creates integration work. DEV.co supplies the software development services that close the gap between syzkaller and a running open-source testing system your team can operate.
Ready to Fuzz Your Kernel?
syzkaller enables automated, coverage-guided kernel testing. Assess your infrastructure, kernel expertise, and OS target before starting. Review setup.md and join the mailing list for guidance. Consider Devco for help integrating fuzzing into your CI/CD and security workflows.