Medium 6.1Published Feb 20, 2026

CVE-2026-27120Leaf-kit html escaping does not work on characters that are part of extended grapheme cluster

Updated under an hour ago (Oct 28, 2026, 3:10 AM ET)

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Every CVE for vapor leaf-kit

Exploited in the last 30 days

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.

CVSS: 6.1 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE): CWE-75, CWE-79, CWE-87
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Feb 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

vapor leaf-kit vapor:leaf_kit (from the name)	before 1.4.1	CNA record
vapor leafkit vapor:leafkit	before 1.14.1	NVD

References

References

https://github.com/vapor/leaf-kit/security/advisories/GHSA-4hfh-fch3-5q7p	x-refsource-confirm, exploit, vendor-advisory
https://github.com/vapor/leaf-kit/commit/8919e39476c3a4ba05c28b71546bb9195f87ef34	x-refsource-misc, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.