CVE-2026-42548
CVE-2026-42548 is a high-severity vulnerability with a CVSS 4.0 base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.
Key facts
- Severity: High (CVSS 4.0 base score 8.6)
- EPSS exploit prediction: 0% (26th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-30147
- Weakness: CWE-79
- Published:
- Last modified:
Description
Flight is an extensible micro-framework for PHP. Prior to 3.18.1, Flight::jsonp() concatenates the ?jsonp= query parameter directly into an application/javascript response body without validating that the value is a legal JavaScript identifier. An attacker can inject arbitrary JavaScript that executes in the response origin, enabling reflected cross-site scripting. This vulnerability is fixed in 3.18.1.
Frequently asked questions
- What is CVE-2026-42548?
- Flight is an extensible micro-framework for PHP. Prior to 3.18.1, Flight::jsonp() concatenates the ?jsonp= query parameter directly into an application/javascript response body without validating that the value is a legal JavaScript identifier. An attacker can inject arbitrary JavaScript that executes in the response origin, enabling reflected cross-site scripting. This vulnerability is fixed in 3.18.1.
- How severe is CVE-2026-42548?
- CVE-2026-42548 has a CVSS 4.0 base score of 8.6, rated high severity.
- Is CVE-2026-42548 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-42548?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-42548 have an EU (EUVD) identifier?
- Yes. CVE-2026-42548 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30147.
- When was CVE-2026-42548 published?
- CVE-2026-42548 was published on 2026-05-13 and last updated on 2026-06-17.
References
Other CWE-79 (Cross-site Scripting (XSS)) vulnerabilities
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- CVE-2022-4361 — Critical (CVSS 10.0): Keycloak, an open-source identity and access management solution, has a cross-site scripting (XSS) vulnerability in the…
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