CVE-2026-40606

mitmproxy is a interactive TLS-capable intercepting HTTP proxy for penetration testers and software developers and mitmweb is a web-based interface for mitmproxy. In mitmproxy 12.2.1 and below, the builtin LDAP proxy authentication does not correctly sanitize the username when querying the LDAP server. This allows a malicious client to bypass authentication. Only mitmproxy instances using the proxyauth option with LDAP are affected. This option is not enabled by default. The vulnerability has been fixed in mitmproxy 12.2.2 and above.

mitmproxy is a interactive TLS-capable intercepting HTTP proxy for penetration testers and software developers and mitmweb is a web-based interface for mitmproxy. In mitmproxy 12.2.1 and below, the builtin LDAP proxy authentication does not correctly sanitize the username when querying the LDAP server. This allows a malicious client to bypass authentication. Only mitmproxy instances using the proxyauth option with LDAP are affected. This option is not enabled by default. The vulnerability has been fixed in mitmproxy 12.2.2 and above.

mitmproxy is a interactive TLS-capable intercepting HTTP proxy for penetration testers and software developers and mitmweb is a web-based interface for mitmproxy. In mitmproxy 12.2.1 and below, the builtin LDAP proxy authentication does not correctly sanitize the username when querying the LDAP server. This allows a malicious client to bypass authentication. Only mitmproxy instances using the proxyauth option with LDAP are affected. This option is not enabled by default. The vulnerability has been fixed in mitmproxy 12.2.2 and above.

### Impact In mitmproxy 12.2.1 and below, the builtin LDAP proxy authentication does not correctly sanitize the username when querying the LDAP server. This allows a malicious client to bypass authentication. Only mitmproxy instances using the `proxyauth` option with LDAP are affected. This option is not enabled by default. ### Patches The vulnerability has been fixed in mitmproxy 12.2.2 and above. ### Acknowledgements We thank Yue (Knox) Liu (@yueyueL) for responsibly disclosing this vulnerability to the mitmproxy team. ### Timeline - **2025-12-08**: Received initial report. - **2025-12-09**: Verified report and confirmed receipt. - **2026-01-02**: Informed researcher that patch will be part of the next regular patch release. - **2026-04-12**: Published patch release and advisory.