CVE-2025-62595: koa Open Redirect — Exploit & Fix

Description

Koa is expressive middleware for Node.js using ES2017 async functions. In versions 2.16.2 to before 2.16.3 and 3.0.1 to before 3.0.3, a bypass to CVE-2025-8129 was discovered in the Koa.js framework affecting its back redirect functionality. In certain circumstances, an attacker can manipulate the Referer header to force a user’s browser to navigate to an external, potentially malicious website. This occurs because the implementation incorrectly treats some specially crafted URLs as safe relative paths. Exploiting this vulnerability could allow attackers to perform phishing, social engineering, or other redirect-based attacks on users of affected applications. This issue has been patched in version 3.0.3.

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CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Weakness Type (CWE)

CWE-601 CWE-601

Affected Products

Vendor	Product	Versions
koajs	koa	3.0.1 — 3.0.3
koajs	koa	All

References

Advisories & Patches

https://github.com/koajs/koa/commit/769fd75cc6b30d72493b370b5a3ae2332ca03c5b https://github.com/koajs/koa/security/advisories/GHSA-g8mr-fgfg-5qpc https://github.com/koajs/koa/security/advisories/GHSA-g8mr-fgfg-5qpc

Exploits

https://github.com/koajs/koa/security/advisories/GHSA-g8mr-fgfg-5qpc https://github.com/koajs/koa/security/advisories/GHSA-g8mr-fgfg-5qpc

Frequently Asked Questions

What is CVE-2025-62595? +

Koa is expressive middleware for Node.js using ES2017 async functions. In versions 2.16.2 to before 2.16.3 and 3.0.1 to before 3.0.3, a bypass to CVE-2025-8129 was discovered in the Koa.js framework affecting its back redirect functionality. In certain circumstances, an attacker can manipulate the Referer header to force a user’s browser to navigate to an external, potentially malicious website. This occurs because the implementation incorrectly treats some specially crafted URLs as safe relative paths. Exploiting this vulnerability could allow attackers to perform phishing, social engineering, or other redirect-based attacks on users of affected applications. This issue has been patched in version 3.0.3. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2025-62595? +

CVE-2025-62595 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-62595? +

CVE-2025-62595 affects products from koajs, specifically: koa. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-62595? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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