CVE-2026-28499 PUBLISHED

LeafKit's HTML escaping may be skipped for Collection values, enabling XSS

Assigner: GitHub_M
Reserved: 27.02.2026 Published: 18.03.2026 Updated: 18.03.2026

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.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
CVSS Score: 6.9

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	Low
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

Product Status

Vendor	vapor
Product	leaf-kit
Versions	Version < 1.14.2 is affected

References

Problem Types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE
CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) CWE
CWE-116: Improper Encoding or Escaping of Output CWE