| パッケージ | 影響を受けるバージョン | 修正済みバージョン |
|---|---|---|
| github.com/Tencent/WeKnora | < 0.3.0全バージョン | 0.3.0 |
| weknora | < 0.3.0 | 0.3.0 |
A DNS rebinding vulnerability in the web_fetch tool allows an unauthenticated attacker to bypass URL validation and access internal resources on the server, including private IP addresses (e.g., 127.0.0.1, 192.168.x.x). By crafting a malicious domain that resolves to a public IP during validation and subsequently resolves to a private IP during execution, an attacker can access sensitive local services and potentially exfiltrate data.
The vulnerability exists because the web_fetch tool lacks complete DNS pinning. The application performs URL validation only once via validateParams(), but the URL is then passed unchanged to the fetchHTMLContent() function, which eventually reaches fetchWithChromedp(). The headless browser (Chromedp) resolves the hostname independently without DNS pinning, allowing a time-of-check-time-of-use (TOCTOU) attack.
Validation phase (first DNS resolution):
if err := t.validateParams(p); err != nil {
// Returns error for private IPs
results[index] = &webFetchItemResult{
err: err,
// ...
}
return
}
Execution phase (second DNS resolution): The original URL (not the resolved IP) is passed through the execution chain:
output, data, err := t.executeFetch(ctx, p)
// Calls fetchHTMLContent(ctx, targetURL) where targetURL is the original hostname
Chromedp execution (vulnerable DNS resolution):
func (t *WebFetchTool) fetchWithChromedp(ctx context.Context, targetURL string) (string, error) {
// targetURL is not DNS-pinned; browser resolves it independently
err := chromedp.Run(ctx,
chromedp.Navigate(targetURL), // Third DNS lookup occurs here
chromedp.WaitReady("body", chromedp.ByQuery),
chromedp.OuterHTML("html", &html),
)
}
The attacker controls a domain that can be configured to return different DNS responses to different queries, enabling them to bypass the initial private IP check and access restricted resources during the actual fetch.
Setup:
[Unit]
Description=DNS Rebinding Test Server
After=network.target
[Service]
Type=simple
User=root
WorkingDirectory=/root/Repos/dns-rebinding-server
ExecStart=/root/.proto/shims/python -u /root/Repos/dns-rebinding-server/server.py --token aleister1102 --domain aleister.ninja --port 53 --global-tracking --ip1 1.1.1.1 --ip2 0.0.0.0 --first-response-count 1 --reset-time 0
Restart=always
RestartSec=3
[Install]
WantedBy=multi-user.target
これらの製品をお使いですか？サイトをスキャンして、脆弱なバージョンが公開されていないか確認しましょう。
無料でサイトをスキャンThis configures the DNS server to:
1.1.1.1 (a public IP) for the first DNS query127.0.0.1 (localhost) for all subsequent queriesThe sequence can also be reset via reset.domain.com (reset to 1.1.1.1).
Note: We may need to reset the sequence as the TOCTOU attack is not truly reliable and needs to be triggered multiple times.
python -m http.server 8888
Execution:
http://attacker.example.com)attacker.example.com → 1.1.1.1 ✓ Passes validationattacker.example.com → 127.0.0.1 ✗ Bypass achievedweb_fetch tool successfully connects to 127.0.0.1:8080 and returns the local server's contentResult: The attacker gains access to the local HTTP server and can read its content, demonstrating that internal resources are now accessible through the rebinding attack.
PoC video:
Vulnerability Type: DNS Rebinding / Server-Side Request Forgery (SSRF)
Who is impacted: