deps: koa [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
koa (source)	3.0.1 -> 3.0.3

GitHub Vulnerability Alerts

CVE-2025-62595

Summary:

A bypass 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 vulnerability affects the code referenced in GitHub Advisory GHSA-jgmv-j7ww-jx2x (which is tracked as CVE‑2025‑54420).

Details:

The patched code attempts to treat values that startWith('/') as safe relative paths and only perform origin checks for absolute URLs. However, protocol‑relative URLs (those beginning with //host) also start with '/' and therefore match the startsWith('/') branch. A protocol‑relative referrer such as //evil.com with trailing double-slash is treated by the implementation as a safe relative path, but browsers interpret Location: //evil.com as a redirect to https://evil.com (or http:// based on context).
This discrepancy allows an attacker to supply Referer: //evil.com and trigger an external redirect - bypassing the intended same‑origin protection.

Proof of concept (PoC):

Affected line of code: https://github.com/koajs/koa/blob/master/lib/response.js#L326
The problematic logic looks like:

Request with a protocol‑relative Referer:
curl -i -H "Referer: //haymiz.dev" http://127.0.0.1:3000/test

Vulnerable response will contain:
HTTP/1.1 302 Found
Location: //haymiz.dev

A browser receiving that Location header navigates to https://haymiz.dev (or http:// depending on context), resulting in an open redirect to an attacker‑controlled host:

Recommendation / Patch:

• Do not treat //host as a safe relative path. Explicitly exclude protocol‑relative values from any relative‑path branch.
• Normalize the Referer by resolving it with a base (e.g., new URL(rawRef, ctx.href)), then compare resolved.origin (scheme+host+port) to ctx.origin (or ctx.host plus scheme/port) before allowing the redirect.

Impact:

An attacker who can cause a victim to visit a specially crafted link (or inject a request with a controlled Referer) can cause the victim to be redirected to an attacker‑controlled domain. This can be used for phishing, social engineering, or to bypass some protection rules that rely on same‑origin navigation.

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Release Notes

koajs/koa (koa)

v3.0.3

Compare Source

What's Changed

• fix: normalize referer before redirect by @​fengmk2 in #​1908

Full Changelog: koajs/koa@v3.0.2...v3.0.3

v3.0.2

Compare Source

What's Changed

• fix: fixes response.attachment behaviour leads to Content-Type Sniffing by @​yowainwright in #​1904
• chore: use NPM trusted publishing with semver tag triggers by @​Copilot in #​1907

New Contributors

• @​Copilot made their first contribution in #​1907

Full Changelog: koajs/koa@v3.0.1...v3.0.2

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