CVE-2026-28807: Gleam-Wisp Wisp

High severity, CVSS 7.5. EPSS: 1.1% chance of exploitation in the next 30 days.

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') vulnerability in gleam-wisp wisp allows arbitrary file read via percent-encoded path traversal. The wisp.serve_static function is vulnerable to path traversal because sanitization runs before percent-decoding. The encoded sequence %2e%2e passes through string.replace unchanged, then uri.percent_decode converts it to .., which the OS resolves as directory traversal when the file is read. An unauthenticated attacker can read any file readable by the application process in a single HTTP request, including application source code, configuration files, secrets, and system files. This issue affects wisp: from 2.1.1 before 2.2.1.

Affected products

• Gleam-Wisp Wisp: from 2.1.1, before 2.2.1 (fixed in 2.2.1)

Published 2026-03-10. Last modified 2026-06-17.