What is CVE-2026-28499?

CVE-2026-28499 is a medium-severity vulnerability in Vapor Leaf-Kit, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-18.

How severe is CVE-2026-28499?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Vapor Leaf-Kit

CVE-2026-28499

LeafKit is a templating language with Swift-inspired syntax. Prior to version 1.14.2, HTML escaping doesn't work correctly when a template prints a collection (Array / Dictionary) via `#(value)`. This can result in XSS, allowing potentially untrusted input to be rendered unescaped. Version 1.14.2 fixes the issue.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.003 (18.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Affected products

Vapor Leaf-kit — versions < 1.14.2
Vapor Leafkit

Weakness classification (CWE)

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC, Release Notes)

Frequently asked questions

What is CVE-2026-28499?: CVE-2026-28499 is a medium-severity vulnerability in Vapor Leaf-Kit, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-18.
How severe is CVE-2026-28499?: Medium severity. CVSS v3 base score is 6.1 out of 10.