CVE-2026-27120

Leaf-kit html escaping does not work on characters that are part of extended grapheme cluster

State: Published
Severity: 6.1 Medium
Published: Feb 20, 2026
Updated: Feb 24, 2026
Reserved: Feb 17, 2026

Description

Leafkit is a templating language with Swift-inspired syntax. Prior to 1.4.1, htmlEscaped in leaf-kit will only escape html special characters if the extended grapheme clusters match, which allows bypassing escaping by using an extended grapheme cluster containing both the special html character and some additional characters. In the case of html attributes, this can lead to XSS if there is a leaf variable in the attribute that is user controlled. This vulnerability is fixed in 1.4.1.

Scores

CVSS	Score	Vector	Source
3.1	6.1 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N	GitHub_M

Weaknesses

CWE-75 Failure to Sanitize Special Elements into a Different Plane (Special Element Injection)
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-87 Improper Neutralization of Alternate XSS Syntax

Affected Products

Product	Versions
leaf-kitvapor	< 1.4.1Affected

References

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