Leafkit
CVE-2026-27120
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V1 - Encoding and Sanitization Failure to sanitize special elements
|
| Impact | CVSS 6.1 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: Required. Public exploit/POC available. |
| Exploit ScenarioDerived | An attacker could exploit this vulnerability to XSS if there is a leaf variable in the attribute that is user controlled. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Leafkit versions up to 1.4.1 contains a vulnerability that allows attackers to XSS if there is a leaf variable in the attribute that is user controlled (CVSS 6.1).
RemediationAI
A vendor patch is available — apply it immediately. Fixed in version 1.4.1.. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
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Technical ContextAI · show details
affects Leafkit. 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.
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Severity by source
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
Lifecycle Timeline
3DescriptionGitHub Advisory
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.
Executive ViewAI
Organizations using Leafkit should be aware of moderate risk from CVE-2026-27120 rated CVSS 6.1. Exploitation could compromise the security of affected deployments. Proof-of-concept code is publicly available. A patch is available and should be applied during regular vulnerability management.
Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.
Exploit-DB