FIPS 140-3 mode is incompatible with GOEXPERIMENT=boringcryp

Error message

FIPS 140-3 mode is incompatible with GOEXPERIMENT=boringcrypto

What it means

Returned by fips140.Supported() when the binary was built with GOEXPERIMENT=boringcrypto (the legacy BoringCrypto module). FIPS 140-3 mode and the older BoringCrypto GOEXPERIMENT are mutually exclusive cryptographic stacks; only one can be authoritative at a time.

Source

Thrown at src/crypto/internal/fips140/fips140.go:62

	// before reading it, but it is unclear whether that would then cause
	// false negatives. For now, FIPS+ASAN doesn't need to work.
	if asanEnabled {
		return errors.New("FIPS 140-3 mode is incompatible with ASAN")
	}

	// See EnableFIPS in cmd/internal/obj/fips.go for commentary.
	// Also, js/wasm and windows/386 don't have good enough timers
	// for the CPU jitter entropy source.
	switch {
	case runtime.GOARCH == "wasm",
		runtime.GOOS == "windows" && runtime.GOARCH == "386",
		runtime.GOOS == "openbsd", // due to -fexecute-only, see #70880
		runtime.GOOS == "aix":
		return errors.New("FIPS 140-3 mode is not supported on " + runtime.GOOS + "-" + runtime.GOARCH)
	}

	if boringEnabled {
		return errors.New("FIPS 140-3 mode is incompatible with GOEXPERIMENT=boringcrypto")
	}

	return nil
}

func Name() string {
	return "Go Cryptographic Module"
}

// Version returns the formal version (such as "v1.0.0") if building against a
// frozen module with GOFIPS140. Otherwise, it returns "latest".
func Version() string {
	// This return value is replaced by mkzip.go, it must not be changed or
	// moved to a different file.
	return "latest" //mkzip:version
}

View on GitHub (pinned to b6b368adc5)

Solutions

Choose one crypto stack: drop GOEXPERIMENT=boringcrypto when enabling GOFIPS140=1, or vice versa.
Audit the build environment (env, Dockerfile, CI matrix, go env GOEXPERIMENT) for stale boringcrypto settings.
For new deployments prefer the native FIPS 140-3 module (no GOEXPERIMENT) over BoringCrypto.

Example fix

# before
GOEXPERIMENT=boringcrypto GOFIPS140=1 go build ./...

# after
GOFIPS140=1 go build ./...

Defensive patterns

Strategy: validation

Validate before calling

if err := fips140.Supported(); err != nil {
    if strings.Contains(err.Error(), "boringcrypto") {
        log.Fatal("FIPS 140-3 mode conflicts with GOEXPERIMENT=boringcrypto; pick one")
    }
    log.Fatalf("FIPS unsupported: %v", err)
}

Try / catch

if err := fips140.Supported(); err != nil {
    return fmt.Errorf("FIPS startup check failed: %w", err)
}

Prevention

Audit go env GOEXPERIMENT and CI image env for boringcrypto.
Migrate fully to native FIPS 140-3 (drop GOEXPERIMENT) before enabling GOFIPS140=1.
Document the chosen crypto stack in the project README.

When it happens

Trigger: Building with GOEXPERIMENT=boringcrypto set (env or go build flags) and then enabling GOFIPS140=1 or calling fips140.Supported().

Common situations: Migrating from BoringCrypto to the new native FIPS module and forgetting to drop GOEXPERIMENT; CI images baked with BoringCrypto globally; corporate base images that set both.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/90b29cc2241e896d. Report an issue: GitHub.