#VU108849 Inefficient regular expression complexity in koa - CVE-2025-25200
Published: May 9, 2025
Vulnerability identifier: #VU108849
Vulnerability risk: Critical
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:U/U:Red
CVE-ID: CVE-2025-25200
CWE-ID: CWE-1333
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
koa
koa
Software vendor:
Koa.js
Koa.js
Description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due Koa uses an evil regex to parse the `X-Forwarded-Proto` and `X-Forwarded-Host` HTTP headers. A remote attacker can pass specially crafted data to the application and perform regular expression denial of service (ReDos) attack.
Remediation
Install updates from vendor's website.
External links
- https://github.com/koajs/koa/blob/master/lib/request.js#L259
- https://github.com/koajs/koa/blob/master/lib/request.js#L404
- https://github.com/koajs/koa/commit/5054af6e31ffd451a4151a1fe144cef6e5d0d83c
- https://github.com/koajs/koa/commit/5f294bb1c7c8d9c61904378d250439a321bffd32
- https://github.com/koajs/koa/commit/93fe903fc966635a991bcf890cfc3427d33a1a08
- https://github.com/koajs/koa/releases/tag/2.15.4
- https://github.com/koajs/koa/security/advisories/GHSA-593f-38f6-jp5m