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GHSA-v8w9-8mx6-g223

MediumCVSS 4.8 / 10
Published Mar 11, 2026·Last modified Mar 13, 2026
Affected Components(0)

No affected components available

Description

Summary

When using parseBody({ dot: true }) in HonoRequest, specially crafted form field names such as __proto__.x could create objects containing a __proto__ property.

If the parsed result is later merged into regular JavaScript objects using unsafe merge patterns, this may lead to prototype pollution in the target object.

Details

The parseBody({ dot: true }) feature supports dot notation to construct nested objects from form field names.

In previous versions, the __proto__ path segment was not filtered. As a result, specially crafted keys such as __proto__.x could produce objects containing __proto__ properties.

While this behavior does not directly modify Object.prototype within Hono itself, it may become exploitable if the parsed result is later merged into regular JavaScript objects using unsafe merge patterns.

Impact

Applications that merge parsed form data into regular objects using unsafe patterns (for example recursive deep merge utilities) may become vulnerable to prototype pollution.

Risk Scores
Base Score
4.8

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
4.4

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.18%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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