High (8.8) in fastify fastify-static. EPSS 1.0% chance of exploitation in the next 30 days. Fixed in fastify-static 4.4.1.
A redirect vulnerability in the `fastify-static` module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect Mozilla Firefox users to arbitrary websites via a double slash `//` followed by a domain: `http://localhost:3000//a//youtube.com/%2e%2e%2f%2e%2e`.A DOS vulnerability is possible if the URL contains invalid characters `curl --path-as-is "http://localhost:3000//^/.."`The issue shows up on all the `fastify-static` applications that set `redirect: true` option. By default, it is `false`.
Severity
CVSS 3.1
8.8 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:H
EPSS
1.0% chance of exploitation in the next 30 days; higher than 63% of CVEs (scores of 2026-10-31)