CVE-2026-109955: Double Decoding of the Same Data in honojs hono
Description
A middleware bypass vulnerability exists in hono versions from 4.12.4 up to but not including 4.13.11. This flaw in the serveStatic middleware allows unauthenticated attackers to bypass prefix middleware by exploiting double decoding of percent-encoded paths, enabling access to static files without authentication checks.
CVSS v4.0
Score 6.9medium
Affected software
honojs
hono
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-109955 affects the hono framework versions >=4.12.4 and <4.13.11. The vulnerability arises from double decoding of the same data in the serveStatic middleware, which leads to a bypass of prefix middleware. Attackers can craft malformed percent-encoded paths that the router matches in encoded form, allowing them to reach static files without triggering authentication middleware. This is an unauthenticated attack vector that exploits path normalization issues in the routing logic.
Potential Impact
An unauthenticated attacker can bypass middleware protections intended to enforce authentication or other access controls on static files. This could lead to unauthorized access to static content that should be protected by middleware, potentially exposing sensitive files or information.
Mitigation Recommendations
Upgrade hono to version 4.13.11 or later where this vulnerability is fixed. The affected versions are >=4.12.4 and <4.13.11. No other mitigation or workaround is indicated in the provided data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-10-13T11:25:25.214Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ace36e12cdf04f65668a68d
Added to database: 10/13/2026, 13:49:21 UTC
Last enriched: 10/13/2026, 14:04:50 UTC
Last updated: 10/13/2026, 18:57:34 UTC
Views: 9
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