CVE-2026-71848 Hono: Algorithmic Complexity DoS in Language Middleware
An attacker can cause excessive CPU consumption and service disruption by sending crafted language tags to applications using the Hono framework's language middleware.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-71848?
CVE-2026-71848 is a medium-severity denial of service vulnerability in honojs hono, published on 7 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-407
Which versions are affected by CVE-2026-71848?
2 open source packages ship an affected version, including hono.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | From 4.12.0 | 4.12.34 |
hono npm | From 4.12.0 | 4.12.34 |
How do I fix CVE-2026-71848?
Upgrade hono to 4.12.34 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-71848 being exploited?
There is no known exploitation of CVE-2026-71848 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-KR37060, ECHO-3479-a34e-1fda, GHSA-54fx-42gc-7vw4, MINI-3gvp-78w5-q7cw, MINI-3wwr-w4xh-84pw, MINI-5596-fxvv-prgm and 8 more.