Open redirect via protocol-relative Referer parsing
Published Oct 21, 2025 · Updated Oct 21, 2025
Open redirect in Koa 2.16.2 and Koa 3.0.1 through 3.0.2 allows remote attackers to redirect users via a crafted Referer header. The back method in lib/response.js treats any Referer beginning with a slash as a relative path and copies protocol-relative values into the Location header. Exploitation requires a victim to reach an application route that invokes ctx.back(), enabling navigation to an attacker-controlled site.
Summary
What happened
Open redirect in Koa 2.16.2 and Koa 3.0.1 through 3.0.2 allows remote attackers to redirect users via a crafted Referer header. The back method in lib/response.js treats any Referer beginning with a slash as a relative path and copies protocol-relative values into the Location header. Exploitation requires a victim to reach an application route that invokes ctx.back(), enabling navigation to an attacker-controlled site.
The record
- CVE
- CVE-2025-62595
- Published
- Oct 21, 2025
- Updated
- Oct 21, 2025
- Vendor
- Koa.js
- Product
- Koa
- Classifications
- CWE-601
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 21, 2025CVE publishedPublication date reported by the CVE source.
- Oct 21, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 2.16.2, < 2.16.3
- Affected versionversion=>= 3.0.1, < 3.0.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Protocol-relative Referer proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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