CVE-2026-69207 Hono: ReDoS in CORS middleware via Access-Control-Request-Headers
Attackers can cause denial of service in Hono applications by sending crafted preflight requests that trigger excessive CPU usage in the CORS 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-2026-69207?
CVE-2026-69207 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. Prior to 4.12.34, the built-in CORS middleware, hono/cors, is vulnerable to a regular expression denial of service (ReDoS). During a preflight OPTIONS request, the middleware parses the attacker-controlled Access-Control-Request-Headers header using a whitespace-tolerant regular expression whose backtracking makes its running time quadratic in the input length. Because the header value is bounded only by the deployment's maximum HTTP header size, a single preflight carrying a long run of whitespace can consume seconds of CPU and block request processing. On runtimes that share one execution thread across requests, this stalls concurrent requests as well, and repeated requests can render the service unresponsive. This affects the default configuration, since the vulnerable path is reached whenever cors() is used with an unset or empty allowHeaders. Applications that set a non-empty allowHeaders are not affected. This issue is fixed in version 4.12.34.
Weakness: CWE-1333
Which versions are affected by CVE-2026-69207?
2 open source packages ship an affected version, including hono.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | All versions | 4.12.34 |
hono npm | All versions | 4.12.34 |
How do I fix CVE-2026-69207?
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-2026-69207 being exploited?
There is no known exploitation of CVE-2026-69207 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-JS09983, ECHO-4b53-f5bc-1b65, GHSA-8j4g-w8fx-2239, MINI-3992-723j-7fqp, MINI-5fmg-h7xv-jfg8, MINI-79mx-fjjc-xxwc and 8 more.