CVE-2026-56763 Hono CVE debrief

Who should care

Developers and administrators using Hono versions prior to 4.12.7 should be aware of this vulnerability and take steps to mitigate it. This includes updating Hono to version 4.12.7 or later, using safe merge patterns when merging parsed results into regular JavaScript objects, and validating and sanitizing form field names to prevent specially crafted input.

Technical summary

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. The vulnerability can be mitigated by updating Hono to version 4.12.7 or later, using safe merge patterns, and validating and sanitizing form field names.

Defensive priority

Medium

Recommended defensive actions

• Update Hono to version 4.12.7 or later
• Use safe merge patterns when merging parsed results into regular JavaScript objects
• Validate and sanitize form field names to prevent specially crafted input
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-11T14:16:22.080Z and has not been modified since then. The NVD entry is currently Received. There is limited information available about the vulnerability, and defenders should verify the affected scope and severity with the vendor. The vulnerability affects Hono versions prior to 4.12.7 and allows for prototype pollution via the __proto__ key in parseBody with dot option enabled.

Official resources