Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.13.5, Hono's query helpers treat a question mark after a literal hash fragment as the start of a query string, so the application can read request parameters that browsers, new URL(), reverse proxies, filtering rules, parameter allow and deny lists, access logging, request validation, and other middleware do not observe. The Cache Middleware removes the fragment when building its cache key, allowing a response influenced by parameters inside the fragment to be stored under a key that omits those parameters and later served to other users. This can bypass filtering and auditing, poison cached responses, and enable stored cross-site scripting when an affected parameter is reflected into cached HTML without escaping. Exploitation requires a runtime and intermediary path that passes a literal hash character through to the request URL; Cloudflare Workers and intermediaries that strip fragments are not affected. This issue is fixed in version 4.13.5.

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Tue, 01 Sep 2026 22:00:00 +0000

Type Values Removed Values Added
Description Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.13.5, Hono's query helpers treat a question mark after a literal hash fragment as the start of a query string, so the application can read request parameters that browsers, new URL(), reverse proxies, filtering rules, parameter allow and deny lists, access logging, request validation, and other middleware do not observe. The Cache Middleware removes the fragment when building its cache key, allowing a response influenced by parameters inside the fragment to be stored under a key that omits those parameters and later served to other users. This can bypass filtering and auditing, poison cached responses, and enable stored cross-site scripting when an affected parameter is reflected into cached HTML without escaping. Exploitation requires a runtime and intermediary path that passes a literal hash character through to the request URL; Cloudflare Workers and intermediaries that strip fragments are not affected. This issue is fixed in version 4.13.5.
Title Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials
Weaknesses CWE-444
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-01T20:22:59.164Z

Reserved: 2026-09-01T16:27:58.128Z

Link: CVE-2026-84363

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-01T21:18:47.173

Modified: 2026-09-01T21:18:47.173

Link: CVE-2026-84363

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses