CVE-2025-62595

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

MEDIUM
6.1
CVSS Score
Published: October 21, 2025 at 04:20 PM UTC
Updated: October 8, 2026 at 11:10 AM UTC
1 product affected across 1 vendorKoa

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.3%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

3.0.1 ≤ v < 3.0.3*2.16.2>= 2.16.2, < 2.16.3>= 3.0.1, < 3.0.3
Affected range stops below 2.16.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.0.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

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

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-601

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