---
id: CVE-2026-71848
title: >-
  Hono is a Web application framework that provides support for any JavaScript
  runtime
summary: >-
  Hono is a Web application framework that provides support for any JavaScript
  runtime. From 4.12.0 to 4.12.33, the languageDetector middleware is vulnerable
  to algorithmic complexity denial of service when processing a crafted language
  ta…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-407
vendor: hono
product: hono
affected:
  - 'hono >= 4.12.0, < 4.12.34'
patched:
  - hono 4.12.34
published: '2026-08-07'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T21:02:22.660'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-71848'
references:
  - url: >-
      https://github.com/honojs/hono/commit/f70e2c31684387b3231cc38512a31df6ca76a1c7
    label: security-advisories@github.com
  - url: 'https://github.com/honojs/hono/releases/tag/v4.12.34'
    label: security-advisories@github.com
  - url: 'https://github.com/honojs/hono/security/advisories/GHSA-54fx-42gc-7vw4'
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-54fx-42gc-7vw4'
tags:
  - nvd
  - ghsa
  - npm
epss: 0.00291
epssPercentile: 0.21977
aliases:
  - GHSA-54fx-42gc-7vw4
ecosystem: npm
ingestedAt: '2026-08-07T19:16:20.279Z'
---

## Overview

Hono is a Web application framework that provides support for any JavaScript runtime. From 4.12.0 to 4.12.33, the languageDetector middleware is vulnerable to algorithmic complexity denial of service when processing a crafted language tag containing a large number of hyphen separated subtags. To implement progressive language tag truncation, normalizeLanguage() repeatedly calls parts.slice(0, i).join('-') for every possible prefix, so the total amount of string processing grows quadratically with the number of subtags. Language values may come from a query parameter, cookie, Accept-Language header, or URL path, depending on the detector configuration, and the default detector order enables query string, cookie, and header detection, so applications using languageDetector() may expose this processing to unauthenticated requests. An attacker may repeatedly send requests containing long, hyphen separated language tags, causing excessive CPU consumption and preventing unrelated requests from being processed. This issue is fixed in version 4.12.34.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-71848)

Affected packages:

- `hono >= 4.12.0, < 4.12.34`

Patched in:

- `hono 4.12.34`

Source: https://github.com/advisories/GHSA-54fx-42gc-7vw4