CVE-2026-42549 — flightphp/core
MEDIUMCVE-2026-42549 is a medium-severity (CVSS 4.4) Path Traversal vulnerability in flightphp/core. A fix is available for flightphp/core — see the affected versions and patch details below.
Flight: Path traversal in `make:controller` CLI creates arbitrary directories outside project root
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42549.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-42549 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
flightphp/coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The make:controller CLI command calls mkdir(..., recursive: true) on a path built from the user-supplied controller name, before Nette's class-name validation runs. The class-file write is correctly rejected by Nette when the name contains /, but the recursive directory creation side effect is already committed — including directories located outside the project root through ../ traversal.
Affected code
flight/commands/ControllerCommand.php (≈ 63-66):
if (is_dir(dirname($controllerPath)) === false) {
$io->info('Creating directory ' . dirname($controllerPath), true);
mkdir(dirname($controllerPath), 0755, true); // un-normalized, runs before validation
}
Proof of concept
$ php vendor/flightphp/runway/runway make:controller '../../../../tmp/CONTROLLER_TRAVERSAL_TEST/pwn'
Creating directory .../app/controllers/../../../../tmp/CONTROLLER_TRAVERSAL_TEST
Nette\InvalidArgumentException: Value '../../../../tmp/CONTROLLER_TRAVERSAL_TEST/pwnController' is not valid class name.
$ ls /home/user/tmp/CONTROLLER_TRAVERSAL_TEST
(directory exists — created before the exception was thrown)
Impact
- Arbitrary directory creation outside the project root, executable by any local actor that can run the Flight CLI (developer machine, shared CI build agent, compromised dev container).
- Primes log-file planting for chained LFI exploitation (e.g. creating a directory where an attacker can later drop a
.phpfile to be included via a distinct template-include weakness). - On Windows, the
\separator opens additional traversal surface.
Patch (fixed in 3.18.1, commit b8dd23a)
The controller name is now normalized with basename() and validated against ^[A-Za-z_][A-Za-z0-9_]*$ before any mkdir side effect runs.
Credit
Discovered by @Rootingg.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | flightphp/core | all versions | 3.18.1composer require flightphp/core:^3.18.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flightphp/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update flightphp/core to 3.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42549 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42549 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-42549. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-42549 in your dependencies?
O3 Security finds CVE-2026-42549 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.