CVE-2026-28499

LeafKit's HTML escaping may be skipped for Collection values, enabling XSS

MEDIUM
6.1
CVSS Score
Published: March 18, 2026 at 01:19 AM UTC
Updated: June 17, 2026 at 10:28 AM UTC
1 product affected across 1 vendorLeafkit

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.3%
SSVC
PoC

Description

LeafKit is a templating language with Swift-inspired syntax. Prior to version 1.14.2, HTML escaping doesn't work correctly when a template prints a collection (Array / Dictionary) via `#(value)`. This can result in XSS, allowing potentially untrusted input to be rendered unescaped. Version 1.14.2 fixes the issue.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.14.2
Affected range stops below 1.14.2, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/vapor/leaf-kit/security/advisories/GHSA-6jj5-j4j8-8473
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/vapor/leaf-kit/releases/tag/1.14.2

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79CWE-80CWE-116

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