CVE-2026-27120CWE-75CWE-79CWE-87

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

Medium · published February 20, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
25.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00333 · 25.5th percentile
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
Published
2026-02-20T21:27Z
EPSS history
Timeline
  • 20 FEB 21:27Z
    Leaf-kit html escaping does not work on characters that are part of extended grapheme cluster
    cvelistv5