Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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Executive Summary

The vulnerability in Hono versions before 4.12.12 occurs because cookie names are not properly validated in the setCookie(), serialize(), and serializeSigned() functions.

This allows invalid characters, such as control characters like carriage return (\r) or newline (\n), to be included in user-controlled cookie names, which can produce malformed Set-Cookie header values.

While modern runtimes like Node.js and Cloudflare Workers reject these invalid headers and cause runtime errors before the response is sent, the main issue is that it affects the correctness and robustness of the application, leading to runtime errors rather than confirmed header injection or response splitting.

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Impact Analysis

This vulnerability primarily impacts the availability and robustness of applications using affected Hono versions.

Because invalid cookie names can cause malformed Set-Cookie headers, modern runtimes reject these headers and trigger runtime errors before responses are sent.

As a result, applications may experience runtime errors leading to availability issues rather than successful exploitation through header injection or response splitting.

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Detection Guidance

This vulnerability involves malformed Set-Cookie header values caused by invalid characters in cookie names, such as carriage return (\r) or newline (\n). Detection can focus on monitoring HTTP responses for malformed Set-Cookie headers containing such control characters.

You can inspect HTTP traffic on your network or system using tools like tcpdump, Wireshark, or curl combined with grep to identify suspicious Set-Cookie headers.

• Use tcpdump to capture HTTP traffic and filter for Set-Cookie headers: tcpdump -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep -i 'Set-Cookie'
• Use curl to make requests to your application and grep for control characters in Set-Cookie headers: curl -i http://your-app-url | grep -P 'Set-Cookie:.*[\r\n]'
• Use Wireshark to capture and analyze HTTP responses, filtering for Set-Cookie headers and checking for invalid characters.

Additionally, review application logs for runtime errors related to header serialization failures, as modern runtimes reject invalid headers causing availability issues.

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Mitigation Strategies

The primary mitigation is to upgrade the Hono framework to version 4.12.12 or later, where the issue with cookie name validation in the setCookie(), serialize(), and serializeSigned() functions has been fixed.

Until the upgrade can be applied, ensure that any user-controlled input used as cookie names is properly sanitized to exclude control characters such as carriage return (\r) and newline (\n).

Monitor your application for runtime errors caused by malformed Set-Cookie headers, as these indicate attempts to exploit the vulnerability.

If possible, implement additional input validation or filtering at the application or web server level to prevent invalid cookie names from being processed.

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