Honojs Hono up to 4.12.33 languageDetector normalizeLanguage resource consumption

Summaryinfo

A vulnerability classified as problematic has been found in Honojs Hono up to 4.12.33. This vulnerability affects the function normalizeLanguage of the component languageDetector. The manipulation leads to resource consumption. This vulnerability is documented as CVE-2026-71848. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Honojs Hono up to 4.12.33. It has been rated as problematic. This issue affects the function normalizeLanguage of the component languageDetector. The manipulation with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-71848 since 08/07/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 4.12.34 eliminates this vulnerability.

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Productinfo

Vendor

• Honojs

Name

• Hono

Version

• 4.12.0
• 4.12.1
• 4.12.2
• 4.12.3
• 4.12.4
• 4.12.5
• 4.12.6
• 4.12.7
• 4.12.8
• 4.12.9
• 4.12.10
• 4.12.11
• 4.12.12
• 4.12.13
• 4.12.14
• 4.12.15
• 4.12.16
• 4.12.17
• 4.12.18
• 4.12.19
• 4.12.20
• 4.12.21
• 4.12.22
• 4.12.23
• 4.12.24
• 4.12.25
• 4.12.26
• 4.12.27
• 4.12.28
• 4.12.29
• 4.12.30
• 4.12.31
• 4.12.32
• 4.12.33

Website

• Product: https://github.com/honojs/hono/

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