Duplicate Advisory: Hono vulnerable to Prototype Pollution possible through __proto__ key allowed in parseBody({ dot: true })
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This advisory has been withdrawn because it is a duplicate of GHSA-v8w9-8mx6-g223.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.
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.