What is CVE-2026-27120?

CVE-2026-27120 is a medium-severity vulnerability in Vapor Leaf-Kit, classified under CWE-75. CVSS score: 6.1/10. Published 2026-02-20.

How severe is CVE-2026-27120?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Vapor Leaf-Kit

CVE-2026-27120

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.

EPSS: 0.002 (14.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Affected products

Vapor Leaf-kit — versions < 1.4.1
Vapor Leafkit

Weakness classification (CWE)

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)

Frequently asked questions

What is CVE-2026-27120?: CVE-2026-27120 is a medium-severity vulnerability in Vapor Leaf-Kit, classified under CWE-75. CVSS score: 6.1/10. Published 2026-02-20.
How severe is CVE-2026-27120?: Medium severity. CVSS v3 base score is 6.1 out of 10.