CVE-2026-42552 is a high-severity (CVSS 7.5) CWE-209 vulnerability in flightphp/core. A fix is available for flightphp/core — see the affected versions and patch details below.
Flight: Sensitive information disclosure via default error handler in flightphp/core
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42552.
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-2026-42552 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 default error handler Engine::_error() writes the full exception message, exception code, and stack trace (including absolute filesystem paths) directly into the HTTP 500 response, with no debug gating. Production deployments leak internal paths, any secret interpolated into an exception message, and full module structure — giving attackers primitives for chaining other weaknesses (LFI, path traversal).
Affected code
flight/Engine.php (≈ lines 678-704):
public function _error(Throwable $e): void
{
...
$msg = sprintf(<<<'HTML'
<h1>500 Internal Server Error</h1>
<h3>%s (%s)</h3>
<pre>%s</pre>
HTML,
$e->getMessage(),
$e->getCode(),
$e->getTraceAsString()
);
$this->response()->cache(0)->clearBody()->status(500)->write($msg)->send();
}
No flight.debug check, no environment gating.
Proof of concept
Any uncaught exception — including those auto-raised from handleError() — returns:
HTTP/1.1 500 Internal Server Error
<h1>500 Internal Server Error</h1>
<h3>secret path /var/www/config/db.yml; token=LEAKED123 (0)</h3>
<pre>#0 [internal function]: {closure}()
#1 /home/user/app/vendor/flightphp/core/flight/core/Dispatcher.php(361)...
#2 /home/user/app/vendor/flightphp/core/flight/Engine.php(...)
...
</pre>
Reproduced against the live PoC app at /poc5/error.
Impact
- Disclosure of absolute filesystem paths (primes weaponization of LFI / path-traversal vulnerabilities in the same application).
- Disclosure of secrets (DB credentials, API tokens) when exceptions are constructed with interpolated configuration values.
- Enumeration of installed vendor packages and internal application structure.
Patch (fixed in 3.18.1, commit b8dd23a)
A new flight.debug setting (default false) gates the verbose output. In production the handler now emits only <h1>500 Internal Server Error</h1>. Developers can set flight.debug = true in local environments to restore the full trace output.
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-2026-42552 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-2026-42552 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-42552. 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-2026-42552 in your dependencies?
O3 Security finds CVE-2026-42552 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.