Vulnerability · Published Mar 18, 2026 · Assigned by GitHub_M
CVE-2026-28499LeafKit's HTML escaping may be skipped for Collection values, enabling XSS
Medium 6.9
In plain English
A medium-severity cross-site scripting in leaf-kit from vapor. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities).
Severity (CVSS 4.0)6.9Medium
Exploit odds (30 days)0.3%top 79.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official 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 products (as reported)
Weakness: CWE-79, CWE-80, CWE-116 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N
References
- https://github.com/vapor/leaf-kit/security/advisories/GHSA-6jj5-j4j8-8473 x_refsource_CONFIRM
- https://github.com/vapor/leaf-kit/commit/6044b844caa858a0c5f2505ac166f5a057c990dc x_refsource_MISC
- https://github.com/vapor/leaf-kit/releases/tag/1.14.2 x_refsource_MISC