# CVE-2026-42548: FlightPHP Flight reflected XSS in Flight::jsonp callback

Source: https://junglewise.ai/threats/cve-2026-42548-flightphp-flight-reflected-xss-in-flight-jsonp-callback  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-13. Updated: 2026-05-14  
License: CC BY 4.0 with a link back

CVE-2026-42548 · Severity: high · CVSS 4 · Published 2026-05-13

Flight is a micro-framework for PHP used to build web applications and APIs. A vulnerability in its JSONP handling allows attackers to inject malicious scripts into web pages. This could lead to unauthorized access to user sessions, theft of sensitive cookies, or the exposure of private API data.

Technologies: [FlightPHP Flight](https://junglewise.ai/threats/technologies/flight), [flightphp/core (Packagist)](https://junglewise.ai/threats/technologies/flightphp-core). Vendors: [FlightPHP](https://junglewise.ai/threats/vendors/flightphp), [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is CVE-2026-42548 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42548 being exploited in the wild.

**How severe is CVE-2026-42548?** High severity, with a CVSS score of 4, published 13 May 2026.

**Which products and versions are affected?** FlightPHP Flight < 3.18.1; FlightPHP Flight core < 3.18.1; flightphp/core (Packagist) < 3.18.1, ECOSYSTEM:introduced=0,fixed=3.18.1.

**Is there a fix for CVE-2026-42548?** Yes. flightphp/core (Packagist): upgrade to 3.18.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-42548 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-42548?** Check whether you run FlightPHP Flight, FlightPHP Flight core or flightphp/core (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- flightphp/core (Packagist): upgrade to 3.18.1 or later

  ```sh
  composer require flightphp/core:^3.18.1
  ```


## Technical details

A reflected Cross-Site Scripting (XSS) vulnerability exists in the `Flight::jsonp()` method within `flight/Engine.php`. The framework concatenates the `jsonp` query parameter directly into the `application/javascript` response body without validating it as a legal JavaScript identifier. A remote attacker can provide a malicious payload in the query string that, when executed in the context of the victim's browser, can steal session cookies or exfiltrate authenticated API responses. The issue is fixed in version 3.18.1 by implementing a regex validation (`^[A-Za-z_$][\w$.]{0,127}$`) for the callback name.

## Affected products

- flightphp core < 3.18.1

## Identifiers

- CVE-2026-42548
- GHSA-fcx8-ph5r-mxr4

## Timeline

- 2026-04-29: disclosed: Initial disclosure in flightphp/core repository
- 2026-05-06: advisory: GitHub Advisory published
- 2026-05-13: other: NVD publication date

## References

- [https://api.github.com/users/Rootingg](https://api.github.com/users/Rootingg)
- [https://github.com/Rootingg](https://github.com/Rootingg)
- [https://api.github.com/users/Rootingg/gists%7B/gist_id%7D](https://api.github.com/users/Rootingg/gists%7B/gist_id%7D)
- [https://api.github.com/users/Rootingg/repos](https://api.github.com/users/Rootingg/repos)
- [https://avatars.githubusercontent.com/u/91620858?v=4](https://avatars.githubusercontent.com/u/91620858?v=4)
- [https://api.github.com/users/Rootingg/events%7B/privacy%7D](https://api.github.com/users/Rootingg/events%7B/privacy%7D)

## Related threats

- [Flight PHP sensitive information disclosure in default error handler](https://junglewise.ai/threats/cve-2026-42552-flight-php-sensitive-information-disclosure-in-default-error)
- [Flight PHP HTTP method override in Request::getMethod](https://junglewise.ai/threats/cve-2026-42551-flight-php-http-method-override-in-request-getmethod)
- [Flight PHP SQL injection in SimplePdo database helper](https://junglewise.ai/threats/cve-2026-42550-flight-php-sql-injection-in-simplepdo-database-helper)
- [Flight PHP path traversal in make:controller CLI command](https://junglewise.ai/threats/cve-2026-42549-flight-php-path-traversal-in-make-controller-cli-command)