VulnerabilityDeferred

CVE-2026-84363

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…

MEDIUM 5.9EPSS 0.34%

Does this matter?

Lower severity and a low EPSS score (0.34%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 5.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS: 0.34% probability · 28th percentile
CISA KEV: Not listed
Weakness: CWE-444
Source: security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.