{"cve":"CVE-2023-49803","nvd":{"published":"2023-12-11T23:15:07.620","modified":"2026-06-17T06:36:29.933","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5},"cwes":["CWE-346"],"references":["https://github.com/koajs/cors/commit/f31dac99f5355c41e7d4dd3c4a80c5f154941a11","https://github.com/koajs/cors/security/advisories/GHSA-qxrj-hx23-xp82","https://github.com/koajs/cors/commit/f31dac99f5355c41e7d4dd3c4a80c5f154941a11","https://github.com/koajs/cors/security/advisories/GHSA-qxrj-hx23-xp82"],"products":["koajs:cross-origin_resource_sharing_for_koa"],"source":"nvd","synced_at":"2026-10-19T21:42:34.585441961+00:00"},"epss":{"cve":"CVE-2023-49803","score":0.00279,"percentile":0.20351,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-qxrj-hx23-xp82","url":"https://osv.dev/vulnerability/GHSA-qxrj-hx23-xp82","summary":"Overly permissive origin policy","modified":"2026-09-10T03:50:04.649565369Z","packages":[{"ecosystem":"npm","name":"@koa/cors","purl":"pkg:npm/%40koa/cors","ranges":["<5.0.0"],"fixed":["5.0.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}