CVE-2026-27120
Leaf-kit html escaping does not work on characters that are part of extended grapheme cluster
MEDIUM 6.1EPSS 0.3%
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.
- Affected
- vapor · leaf-kit
- CVSS v3.1 GITHUB
- 6.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - EPSS
- 0.33% chance of exploitation in the next 30 days, 25th percentile
- Published
- 2026-02-20
- Updated
- 2026-02-24
Proof-of-concept exploits (1)
Security advisories
- vapor/leaf-kit/security/advisories/GHSA-4hfh-fch3-5q7p
- vapor/leaf-kit/commit/8919e39476c3a4ba05c28b71546bb9195f87ef34