5.9

CVE-2026-6414: fastify fastify-static

CVSS: 5.9v3.1MediumAnalyzed
AliasesGHSA-x428-ghpx-8j92
Published 16-04-2026Last modified 16-04-2026
Open JSON

Vulnerability summary

CVE-2026-6414 is a medium (CVSS 5.9) vulnerability in fastify fastify-static. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 37.6% of scored vulnerabilities.

Overall risk
24/100
0100
Low · default modelHow is this calculated?
CVSS score
5.9/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.45%
0%100%
Low · +0.03 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 2
CVE-2026-22031CVE-2026-29045

Timeline

  1. 16-04-2026
    PublishedVulnerability first disclosed.
  2. 16-04-2026
    Last modifiedVulnerability information updated.

Description

@fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution, while Fastify's router treats them as literal characters. This mismatch allows attackers to bypass route-based middleware or guards that protect files served by @fastify/static. For example, a route guard on a protected path can be circumvented by encoding the path separator in the URL. Upgrade to @fastify/static 9.1.1 to fix this issue. There are no workarounds.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.45%

Chance of exploitation in the next 30 days

Percentile

38%

Versus all other CVEs

30-day change

+0.03 pp

From 0.41% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.45%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

@fastify1 product
  • static≥ 8.0.0, < 9.1.1
@fastify/static1 product
Fastify1 product

3 vendors · 3 products

References

6 links