Authentication bypass using an alternate path or channel in hono - CVE-2026-126357
Published: November 10, 2026 / Updated: November 13, 2026
Vulnerability identifier: #VU164377
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-126357
CWE-ID: CWE-288
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass authentication middleware and access protected information in a mounted application.
The vulnerability exists due to incorrect dynamic-prefix length calculation and re-normalization of decoded paths in Hono's mount() and app.mount() when forwarding requests to mounted applications. A remote attacker can request /api/a/xxxxx/admin/secret under a /api/:tenant/* mount or /app/public%5C..%5Cadmin/secret under an /app mount to reach /admin/secret without triggering the outer application's path-scoped authentication middleware.
Affected software
hono
How to mitigate CVE-2026-126357
Install security update from vendor's website.
hono - update to 4.13.16