CVE-2025-62595

Koa Vulnerable to Open Redirect via Trailing Double-Slash (//) in back Redirect Logic

Published Oct 21, 2025 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-g8mr-fgfg-5qpc Koa Vulnerable to Open Redirect via Trailing Double-Slash (//) in back Redirect Logic
History
Type Values Removed Values Added
CPEs cpe:2.3:a:koajs:koa:*:*:*:*:*:node.js:*:*
cpe:2.3:a:koajs:koa:2.16.2:*:*:*:*:node.js:*:*
Type Values Removed Values Added
First Time appeared Koajs
Koajs koa
Vendors & Products Koajs
Koajs koa
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Koa Vulnerable to Open Redirect via Trailing Double-Slash (//) in back Redirect Logic
Weaknesses CWE-601
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 21, 2025, 4:35 PM
Reserved
Oct 16, 2025, 7:24 PM
Status
Analyzed
Published
Oct 21, 2025, 5:15 PM
Modified
Oct 8, 2026, 11:10 AM
Severity
Moderate
Public date
Oct 21, 2025, 4:20 PM