SSRF Bypass in V Framework via Parser Differential

Executive Summary

This vulnerability is a server-side request forgery (SSRF) bypass in V through version 0.5.2. It occurs due to a parser differential between net.urllib and net.http. Attackers can exploit this by crafting a URL with a backslash in the authority section. net.urllib.parse() extracts the trusted host for allowlist validation, while net.http.get() normalizes the backslash and connects to an internal host, bypassing host-based allowlists to access restricted internal network services.

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Detection Guidance

Detecting this SSRF bypass vulnerability requires checking for unusual URL parsing behavior in applications using net.urllib and net.http libraries. Monitor network logs for requests containing backslashes in the authority section of URLs. Test applications by sending crafted URLs with backslashes to see if internal hosts are accessed despite allowlist restrictions.

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Impact Analysis

This vulnerability allows attackers to access internal network services that were intended to be blocked by allowlists. This could lead to unauthorized data exfiltration, internal service manipulation, or further network compromise, depending on the exposed services.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. Organizations may face compliance violations, legal penalties, and reputational damage due to potential data breaches or unauthorized access to protected health or personal information.

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Mitigation Strategies

Immediately update the affected library to the fixed commit 85859f0. Implement strict input validation for URLs, rejecting any containing backslashes in the authority section. Review and tighten network allowlists to ensure they cannot be bypassed. Monitor network traffic for suspicious internal requests.

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