CVE-2026-109955: Hono 4.12.4 before 4.13.11 Middleware Bypass via serveStatic Double Decoding

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-13 · updated 2026-10-13
Weakness: CWE-174

Description

Hono from 4.12.4 before 4.13.11 contains a middleware bypass vulnerability in serveStatic that allows unauthenticated attackers to skip prefix middleware by exploiting double path decoding. Attackers can send malformed percent-encoded paths that the router matches in encoded form, reaching static files without authentication checks running.

Affected products

honojs hono: from 4.12.4 before 4.13.11 — fixed in 4.13.11

How to fix

Upgrade to a fixed version: honojs hono 4.13.11. Check the vendor advisory for mitigations.

References

https://github.com/honojs/hono/security/advisories/GHSA-5r4p-p66f-jhc7
https://www.vulncheck.com/advisories/hono-4.12.4-before-4.13.11-middleware-bypass-via-servestatic-double-decoding

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