We crash your code before attackers do.
APEX writes the fuzz harness with AI, runs your C, C++ and Rust until it breaks, and hands back the exact input that did it — the buffer overflows and use-after-frees behind real remote takeover. Every finding ships with a crash you can replay. You pay per run.
Three promises on every run
Not a feature list — the three things you get proof of, every single run.
We write the harness
Fuzzing without a fuzzing engineer. An LLM builds the harness that feeds the fuzzer — the weeks-long expert step every other tool leaves to you.
We prove it
Every finding ships with the exact input that reproduces the crash and an AddressSanitizer trace. You merge on a bug you can run — never on a severity guess.
We stop on purpose
APEX ends the run when the next bug costs far more to find than the last, and you set a hard cap. Two brakes on your spend — we never milk your compute.
One crash, start to finish
A heap buffer overflow APEX found, proved with the crashing input, and fixed — with that input frozen as a test.
Finding · proven
parse.c:184 · reachable from decode_frame()
Reproducing crash input
Fix · pull request
Start free. Pay only for the deep fuzzing.
Scan runs in your CI. Fuzz runs in our cloud, free until your first real crash. Run is the paid tier, billed per run. No seats, no subscription.
APEX Scan
- Flags unchecked memcpy, strcpy, unbounded copies
- Shows which reachable functions are still un-fuzzed
- Writes SARIF to the GitHub Security tab
- Runs as a GitHub Action. Nothing installed.
APEX Fuzz
- AI writes the harness — no fuzzing engineer needed
- Coverage-guided fuzzing until the first reproducing crash
- Free up to that first proven bug, on our compute
- You see it is real before you pay a cent
APEX Run
- Coverage-guided + concolic, sanitizers on
- Minimizes the crash and opens a fix pull request
- The crashing input is frozen as a regression test
- Credits meter compute. Hard per-run cap you set.
Harness, fuzz, prove, fix
Every crash arrives as a pull request for a person to review. Nothing merges on its own.
Harness
An LLM reads your functions and writes the fuzz harness — the step teams skip because it needs a specialist.
Fuzz
Coverage-guided, millions of inputs, sanitizers on, until the program crashes or corrupts memory.
Prove
The exact crashing input comes back with an AddressSanitizer trace. You can replay it and watch it break.
Fix
A pull request with the bounds or lifetime fix, and the crashing input frozen as a regression test.
The bugs behind the worst breaches
Buffer overflows and use-after-free are how one bad input becomes remote code execution — the class behind Heartbleed and a steady stream of critical RCE in routers, VPNs and media libraries. If your product runs close to the metal and takes untrusted input, this is the risk that ends in a headline.
- Findings tied to attacker-reachable input paths, not theoretical warnings
- Sanitizer-grade detection: overflow, use-after-free, OOB, leaks
- The crash arrives with the exact bytes that trigger it
Automotive — ISO/SAE 21434
Names fuzz testing as a required method for higher-assurance components; UN R155 is binding across UNECE markets.
Medical — FDA premarket
Fuzz testing is one of the security activities expected in a device cybersecurity submission.
Critical infra — CISA
Vendors in memory-unsafe languages are asked to publish a memory-safety roadmap. The clock is public.
The fuzzer writes its own harness
Every team can run a fuzzer. Almost none do — because someone has to hand-write the harness that feeds it, and that someone is a fuzzing specialist, weeks per target. That single cost is why most companies ship the bugs. APEX generates the harness with an LLM, so you go from repo to crashes without hiring for it.
- No fuzzing engineer on staff required
- Fresh harnesses as your code changes
- Reaches under-fuzzed paths hand-written harnesses miss
A crash you can replay for every finding. A test that keeps it fixed.
APEX attaches the exact input that reproduces the crash and freezes it as a regression test — it fails before the fix and passes after. You review the pull request and merge on that, not on a severity score.
- The input is concrete bytes, minimized and reproducible
- The test re-runs on every commit, so the bug cannot come back
- A person reviews the pull request. No auto-merge.
Your private code stays yours
The free public fuzzers only take open source. APEX is built for the code you cannot upload — and it runs where that code already lives.
Runs on private code
The thing Google's free service will not do: fuzz your proprietary product. Self-hosted or air-gapped, your source never leaves your infrastructure.
Bring your own LLM key
The models that write the harness can run on your company's key.
Never used for training
Your code, crashes and findings are never used to train anything, by us or anyone else.
Audited
SOC 2 Type II in progress. We fuzz our own engine before every release.
No seats. No subscription. Pay per run.
Scan is free in CI. Fuzz is free until your first real crash. Run is metered in credits for compute, with a hard per-run cap you set.
- Unsafe memory operations
- Reachable-but-un-fuzzed functions
- SARIF to the GitHub Security tab
- AI writes the harness for you
- Coverage-guided fuzzing in our cloud
- A reproducing crash input, free
- Everything free, plus concolic + minimization
- Fix PR with the crash frozen as a test
- Self-host, air-gap, SSO, SLA
A hard cap you set
Every paid run stops at the credit ceiling you choose up front. You are never billed past it.
APEX stops on its own
The run ends when the next crash costs far more to find than the last. We don't run up your compute to run up your bill.
How APEX compares
Free engines are raw kits. Static tools read code but never run it. APEX fuzzes your private code, writes the harness, and proves the crash.
| Capability | APEX | OSS-Fuzz / AFL++ | Mayhem | Snyk / Semgrep / CodeQL |
|---|---|---|---|---|
| Fuzzes your private code | Yes | Public OSS only | Yes | Reads it |
| Writes the fuzz harness for you | Yes · AI | Hand-written | Partial | n/a |
| Reproducing crash input per finding | Yes | Yes | Yes | No |
| Finds memory-safety at runtime | Yes | Yes | Yes | Static only |
| Managed infra, no ops | Yes | Self-run | Yes | Yes |
| Ships the fix as a PR + test | Yes | No | No | Autofix |
| Pricing model | Per run | Free (public) | Enterprise | Per developer |
OSS-Fuzz and AFL++ are excellent — and free — if your code is open source and you have an engineer to write and run the harnesses. Mayhem proved the enterprise case and was acquired in late 2025. Snyk, Semgrep and CodeQL are mature static analyzers with huge rule libraries. APEX is for the gap they leave: fuzzing private code with a crash you can replay on every finding — priced per run.
Find a real bug, earn the CVE
When APEX confirms a memory bug in an open-source library, it drafts a private advisory with the crashing input attached. You file it through a GitHub advisory under your own name. The reporter credit goes to you.
- Every submission carries a reproducing crash input
- Private first, approved by a person, never auto-filed
- Your name is on the finding
Fuzz your repo before someone else does
Free to your first crash. No card. Private code stays in your infrastructure.