CVE-2026-71848
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk21th percentile - higher than 21% of all known CVEs
Summary
A vulnerability in the Hono framework from version 4.12.0 to 4.12.33 affects the languageDetector middleware, which is vulnerable to algorithmic complexity denial of service when processing a crafted language tag with a large number of hyphen-separated subtags. The normalizeLanguage() function repeatedly calls parts.slice(0, i).join('-') for every possible prefix, causing quadratic processing growth. The issue is fixed in version 4.12.34.
Risk Assessment
The risk is CPU exhaustion by an unauthenticated attacker, potentially preventing processing of other requests and leading to service unavailability.
Recommendation
Upgrade Hono to version 4.12.34 or later and limit language tag length in configuration.
Original NVD description (English source)
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.