CVE-2026-28807 Path Traversal in wisp.serve_static allows arbitrary file read
An unauthenticated attacker can read arbitrary files via percent-encoded path traversal in the wisp.serve_static function.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-28807?
CVE-2026-28807 is a high-severity path traversal vulnerability in gleam-wisp wisp, published on 10 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-22
Which versions are affected by CVE-2026-28807?
3 open source packages ship an affected version, including wisp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
wisp Hex | From 2.1.1 | 2.2.1 |
wisp Hex | From 2.1.1 | 2.2.1 |
wisp Hex | From 2.1.1 | 2.2.1 |
Products include Gleam-Wisp Wisp.
How do I fix CVE-2026-28807?
Upgrade wisp to 2.2.1 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-28807 being exploited?
There is no known exploitation of CVE-2026-28807 in the wild and no public exploit code.
Other vulnerabilities in gleam-wisp wisp
Sources
Also known as EEF-CVE-2026-28807, GHSA-h7cj-j2vv-qw8r.