# Duplicate Advisory: Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })

Source: https://junglewise.ai/threats/duplicate-advisory-hono-vulnerable-to-prototype-pollution-possible-18a2fd74  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-11  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4.8 · Published 2026-07-11

## Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-v8w9-8mx6-g223. This link is maintained to preserve external references.

## Original Description

Hono before 4.12.7 allows __proto__ key in parseBody with dot option enabled, permitting specially crafted form field names to create objects with __proto__ properties. When parsed results are merged into regular JavaScript objects using unsafe merge patterns, attackers can exploit this to achieve prototype pollution and modify object behavior.

Technologies: [hono (npm)](https://junglewise.ai/threats/technologies/hono). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 4.8, published 11 July 2026.

**Which products and versions are affected?** hono (npm) < 4.12.7.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected?** Check whether you run hono (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- hono (npm) < 4.12.7

## Related threats

- [Hono: `css` helper does not escape a closing tag split between the template and an interpolated value, allowing HTML injection](https://junglewise.ai/threats/cve-2026-126359-hono-css-helper-does-not-escape-a-closing-tag-split-between-the)
- [Hono RegExpRouter middleware bypass via wildcard matching](https://junglewise.ai/threats/cve-2026-126358-hono-regexprouter-skips-wildcard-middleware-for-some-route-sets)
- [Hono mount() path traversal bypasses middleware scoping](https://junglewise.ai/threats/cve-2026-126357-hono-mount-and-app-mount-can-forward-a-path-that-bypasses)
- [Hono validator form multipart/form-data parameter bypass](https://junglewise.ai/threats/cve-2026-126356-hono-validator-form-skips-validation-for-multipart-form-data)
- [Hono csrf() middleware bypass via hyperlink auditing](https://junglewise.ai/threats/cve-2026-126355-hono-csrf-does-not-check-requests-sent-by-hyperlink-auditing)