CVE-2023-49803 @koa/cors has overly permissive origin policy
The @koa/cors library disables Same Origin Policy by reflecting request origins when no allowed origin is configured, exposing users to cross-origin attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-49803?
CVE-2023-49803 is a high-severity vulnerability in koajs cors, published on 11 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
@koa/cors npm provides Cross-Origin Resource Sharing (CORS) for koa, a web framework for Node.js. Prior to version 5.0.0, the middleware operates in a way that if an allowed origin is not provided, it will return an `Access-Control-Allow-Origin` header with the value of the origin from the request. This behavior completely disables one of the most crucial elements of browsers - the Same Origin Policy (SOP), this could cause a very serious security threat to the users of this middleware. If such behavior is expected, for instance, when middleware is used exclusively for prototypes and not for production applications, it should be heavily emphasized in the documentation along with an indication of the risks associated with such behavior, as many users may not be aware of it. Version 5.0.0 fixes this vulnerability.
Weakness: CWE-346
Which versions are affected by CVE-2023-49803?
2 open source packages ship an affected version, including @koa/cors. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@koa/cors npm | All versions | 5.0.0 |
@koa/cors npm | All versions | 5.0.0 |
Products include Koajs Cross-Origin Resource Sharing for Koa.
How do I fix CVE-2023-49803?
Upgrade @koa/cors to 5.0.0 or later.
Is CVE-2023-49803 being exploited?
There is no known exploitation of CVE-2023-49803 in the wild and no public exploit code.
Sources
Also known as CLSA-2026-1789052857, GHSA-qxrj-hx23-xp82.