HTTP/HTTPS Traffic Interception Bypass in mad-proxy

Vulnerability

Overview

CVE-2025-67485 affects mad-proxy, a Python-based HTTP/HTTPS proxy server designed for detection and blocking of malicious web activity using custom security policies. In versions 0.3 and below, the proxy fails to properly enforce its traffic interception rules, allowing attackers to bypass the intended inspection and blocking mechanisms. This flaw stems from insufficient validation or handling of certain HTTP/HTTPS requests, enabling them to evade the policy engine entirely [1][2].

Exploitation

An attacker can exploit this vulnerability by sending specially crafted HTTP/HTTPS requests that are not correctly processed by the proxy's rule engine. The attack does not require authentication or special privileges, as the proxy is typically deployed as a transparent or forward proxy.forward proxy intercepting all traffic. The bypass can be triggered remotely, making it accessible to any adversary who can send traffic through the affected proxy instance [3].

Impact

Successful exploitation allows an attacker to circumvent the security policies defined in the proxy's YAML configuration, such as domain block/allow rules. This means malicious traffic—including connections to known command-and-control servers, phishing sites, or other dangerous destinations—can pass through undetected and unblocked. Consequently, sensitive data may be exfiltrated, and the protected network remains exposed to threats that the threats the proxy was intended to mitigate [1][3].

Mitigation

Status

As of the publication date, no official fix is available for CVE-2025-67485. The vendor advisories indicate that the issue is addressed in version 0.4 of mad-proxy, which fixes a related HTTPS interception bypass (CVE-2025-61767). Users are strongly advised to upgrade to v0.4 or later to remain protected [2][3].