# CVE-2026-44457: hono — Fixed in 4.12.18

📦

📦 npm

Not in CISA KEV

MEDIUM severity

# CVE-2026-44457 — hono

MEDIUM 

CVE-2026-44457 is a medium-severity (CVSS 5.3) CWE-524 vulnerability in hono. A fix is available for hono — see the affected versions and patch details below.

Hono: Cache Middleware ignores Vary: Authorization / Vary: Cookie leading to cross-user cache leakage

Also known as[GHSA-p77w-8qqv-26rm](/vulnerability/GHSA-p77w-8qqv-26rm)

Published

May 13, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44457.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs10th percentile — riskier than 10% of all scored CVEsHighest risk

0.00%0.28%0.55%0.83%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

7Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

`hono`npm

104.5Mdownloads / week

## Description

#### Summary

Cache Middleware does not skip caching for responses that declare per-user variance via `Vary: Authorization` or `Vary: Cookie`. As a result, a response cached for one authenticated user may be served to subsequent requests from different users.

#### Details

The Cache Middleware skips caching when a response carries `Vary: *`, certain `Cache-Control` directives (`private`, `no-store`, `no-cache`), or `Set-Cookie`. However, `Vary: Authorization` and `Vary: Cookie` — the standard signals defined in RFC 9110 / RFC 9111 to indicate per-user responses — are not treated as cache-skip reasons.

This issue arises when applications use the Cache Middleware on endpoints that return user-specific data and rely on `Vary: Authorization` or `Vary: Cookie` to scope the response per user, without also setting `Cache-Control: private`.

#### Impact

A user may receive a cached response that was originally generated for a different authenticated user. This may lead to:

-   Disclosure of personally identifiable information or other user-specific data present in the response body
-   Inconsistent or incorrect behavior in user-specific endpoints

This issue affects applications that use the Cache Middleware on endpoints whose responses vary by `Authorization` or `Cookie` and that do not also set `Cache-Control: private`.

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

📦npm

`hono` 

all versions

4.12.18`npm install hono@4.12.18`

## Affected Products

1 product · 1 configurations

Application

`hono`hono

< 4.12.18

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hono, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update hono to 4.12.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44457 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
    

## Frequently Asked Questions

\### Summary Cache Middleware does not skip caching for responses that declare per-user variance via \`Vary: Authorization\` or \`Vary: Cookie\`. As a result, a response cached for one authenticated user may be served to subsequent requests from different users. ### Details The Cache Middleware skips caching when a response carries \`Vary: \*\`, certain \`Cache-Control\` directives (\`private\`, \`no-store\`, \`no-cache\`), or \`Set-Cookie\`. However, \`Vary: Authorization\` and \`Vary: Cookie\` — the standard signals defined in RFC 9110 / RFC 9111 to indicate per-user responses — are not treated as cache-skip r

O3 Security · Impact-Aware SCA

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