What is the CVSS score of CVE-2026-27120?

CVE-2026-27120 has a CVSS 3.1 base score of 6.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Leafkit are affected by CVE-2026-27120?

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.. A patch is available.

Is there a public PoC exploit available for CVE-2026-27120?

Yes, a public proof-of-concept exploit is available for CVE-2026-27120. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-27120?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Leafkit CVE-2026-27120

MEDIUM

Failure to Sanitize Special Elements into a Different Plane (Special Element Injection) (CWE-75)

2026-02-20 security-advisories@github.com

XSS Leafkit

6.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.1 MEDIUM

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

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:04 vuln.today

PoC Detected

Mar 02, 2026 - 13:34 vuln.today

Public exploit code

Patch released

Mar 02, 2026 - 13:34 nvd

Patch available

CVE Published

Feb 20, 2026 - 22:16 nvd

MEDIUM 6.1

DescriptionGitHub 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.

AnalysisAI

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).

Technical ContextAI

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.

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.