CVE-2026-28807

Path Traversal in wisp.serve_static allows arbitrary file read

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

gleam-wisp · wisp

CVSS v4.0 CNA

8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS v4.0 GitHub

8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS v3.1 NVD

7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

1.06% chance of exploitation in the next 30 days, 64th percentile

Published

2026-03-10

Updated

2026-04-06

Proof-of-concept exploits (1)

• advisories/GHSA-h7cj-j2vv-qw8r

Security advisories

• 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
• gleam-wisp/wisp/commit/161118c431047f7ef1ff7cabfcc38981877fdd93

References

• CVE Record
• NVD entry