CVE-2026-27120
Leaf-kit html escaping does not work on characters that are part of extended grapheme cluster
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.
INFO
Published Date :
Feb. 20, 2026, 10:16 p.m.
Last Modified :
Feb. 20, 2026, 10:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-27120
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE |
Solution
- Update Leafkit to version 1.4.1 or later.
- Ensure all user-controlled variables are properly escaped.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27120.
| URL | Resource |
|---|---|
| https://github.com/vapor/leaf-kit/commit/8919e39476c3a4ba05c28b71546bb9195f87ef34 | |
| https://github.com/vapor/leaf-kit/security/advisories/GHSA-4hfh-fch3-5q7p |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27120 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27120
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27120 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-27120 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Feb. 20, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Added CWE CWE-79 Added CWE CWE-75 Added CWE CWE-87 Added Reference https://github.com/vapor/leaf-kit/commit/8919e39476c3a4ba05c28b71546bb9195f87ef34 Added Reference https://github.com/vapor/leaf-kit/security/advisories/GHSA-4hfh-fch3-5q7p