CVE-2026-24472: Hono Cache Information Disclosure Flaw

CVE-2026-24472 Overview

CVE-2026-24472 is an information disclosure vulnerability in Hono, a popular Web application framework that provides support for any JavaScript runtime. The vulnerability exists in the Cache Middleware component, which improperly handles HTTP cache control directives. Specifically, the middleware fails to respect standard cache control headers such as Cache-Control: private or Cache-Control: no-store, which may result in private or authenticated responses being cached and subsequently exposed to unauthorized users.

This vulnerability is classified under CWE-524 (Use of Cache Containing Sensitive Information), as the caching mechanism stores sensitive data that should not be persisted or shared across user sessions.

Critical Impact

Private or authenticated responses may be cached and exposed to unauthorized users, potentially leading to sensitive data leakage including session tokens, personal information, or other confidential data intended for specific authenticated users.

Affected Products

• Hono versions prior to 4.11.7
• Applications using Hono's Cache Middleware
• Any JavaScript runtime environment running vulnerable Hono versions

Discovery Timeline

• 2026-01-27 - CVE-2026-24472 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-24472

Vulnerability Analysis

The vulnerability stems from the Cache Middleware's failure to properly interpret and honor HTTP cache control directives. When a response includes headers such as Cache-Control: private or Cache-Control: no-store, compliant caching implementations should either store the response only in a private cache (for the specific user) or not cache the response at all, respectively.

In affected versions of Hono, the Cache Middleware ignores these directives and caches responses indiscriminately. This creates a scenario where authenticated or user-specific responses can be stored in the cache and subsequently served to different users who request the same resource, effectively bypassing authentication and authorization controls at the caching layer.

The attack can be performed over the network without requiring authentication, making it accessible to any attacker who can send requests to the vulnerable application. However, the impact is limited to confidentiality exposure of cached data.

Root Cause

The root cause of CVE-2026-24472 is improper validation and handling of HTTP cache control headers within Hono's Cache Middleware. The middleware implementation did not include logic to parse and respect the Cache-Control header values that indicate a response should not be cached or should only be stored in private caches. This oversight allowed all responses to be cached regardless of the explicit caching instructions provided by the application.

Attack Vector

The attack vector is network-based and does not require any privileges or user interaction. An attacker can exploit this vulnerability through the following sequence:

1. An authenticated user makes a request to a protected endpoint that returns sensitive data with Cache-Control: private or Cache-Control: no-store headers
2. The vulnerable Cache Middleware ignores these headers and caches the response
3. An unauthenticated attacker (or different user) requests the same resource
4. The cached response containing the first user's sensitive data is served to the attacker

The vulnerability exploitation does not require sophisticated techniques. See the GitHub Security Advisory GHSA-6wqw-2p9w-4vw4 for detailed technical information on the vulnerability mechanism and exploitation scenarios.

Detection Methods for CVE-2026-24472

Indicators of Compromise

• Unexpected cache hits for authenticated or user-specific endpoints that should not be cached
• User reports of seeing other users' data or session information
• Cache entries containing sensitive data with Cache-Control: private or Cache-Control: no-store in the original response headers
• Anomalous patterns in application logs showing cached responses served for authenticated endpoints

Detection Strategies

• Review application dependencies and verify Hono version is 4.11.7 or later
• Audit cache middleware configuration and behavior in staging environments
• Implement monitoring for cache hit ratios on authenticated endpoints that should not be cached
• Test cache behavior by sending requests with various Cache-Control headers and verifying compliance

Monitoring Recommendations

• Enable detailed logging for cache operations including cache keys, hit/miss status, and response headers
• Monitor for unusual patterns where multiple users receive identical responses for personalized endpoints
• Set up alerts for cache entries that contain authentication tokens or user-specific identifiers
• Implement periodic security scans to detect vulnerable dependency versions

How to Mitigate CVE-2026-24472

Immediate Actions Required

• Upgrade Hono to version 4.11.7 or later immediately
• Review cached data and purge any potentially sensitive cached entries
• Audit endpoints that handle authenticated or user-specific data to ensure proper cache control headers are set
• Consider temporarily disabling the Cache Middleware until the patch can be applied

Patch Information

The vulnerability has been addressed in Hono version 4.11.7. The fix ensures that the Cache Middleware properly respects HTTP cache control directives including Cache-Control: private and Cache-Control: no-store.

For patch details, see the GitHub commit 12c5117.

To update, run the appropriate command for your package manager:

# npm
npm update hono

# yarn
yarn upgrade hono

# pnpm
pnpm update hono

Workarounds

• Disable the Cache Middleware entirely for routes that serve authenticated or sensitive data
• Implement a custom caching layer that properly respects cache control headers
• Add a middleware before the Cache Middleware to intercept and bypass caching for sensitive responses
• Use edge caching solutions that properly implement HTTP cache control semantics

# Verify your Hono version
npm list hono

# Force upgrade to the patched version
npm install hono@4.11.7 --save