Mitmweb API Authentication Bypass Using Proxy Server

Open Source Vulnerabilities GHSA-wg33-5h85-7q5p

### Impact In mitmweb 11.1.0 and below, a malicious client can use mitmweb's proxy server (bound to `*:8080` by default) to access mitmweb's internal API (bound to `127.0.0.1:8081` by default). In other words, while the client cannot access the API directly (good), they can access the API through the proxy (bad). An attacker may be able to escalate this [SSRF](https://en.wikipedia.org/wiki/Server-side_request_forgery)-style access to remote code execution. The mitmproxy and mitmdump tools are unaffected. Only mitmweb is affected. The `block_global` option, which is enabled by default, blocks connections originating from publicly-routable IP addresses in the proxy. The attacker needs to be in the same local network. ### Patches The vulnerability has been fixed in mitmproxy 11.1.2 and above. ### Acknowledgements We thank Stefan Grönke (@gronke) for reporting this vulnerability as part of a security audit by [Radically Open Security](https://www.radicallyopensecurity.com/). This audit was supported by the [NGI0 Entrust fund](https://nlnet.nl/entrust/) established by [NLnet](https://nlnet.nl/). ### Timeline - **2025-01-14**: Received initial report. - **2025-01-14**: Verified report and confirmed receipt. - **2025-01-19**: Shared patch with researcher. - **2025-02-04**: Received final confirmation that patch is working. - **2025-02-05**: Published patched release and advisory.

Open Source Vulnerabilities PYSEC-2026-1630

### Impact In mitmweb 11.1.0 and below, a malicious client can use mitmweb's proxy server (bound to `*:8080` by default) to access mitmweb's internal API (bound to `127.0.0.1:8081` by default). In other words, while the client cannot access the API directly (good), they can access the API through the proxy (bad). An attacker may be able to escalate this [SSRF](https://en.wikipedia.org/wiki/Server-side_request_forgery)-style access to remote code execution. The mitmproxy and mitmdump tools are unaffected. Only mitmweb is affected. The `block_global` option, which is enabled by default, blocks connections originating from publicly-routable IP addresses in the proxy. The attacker needs to be in the same local network. ### Patches The vulnerability has been fixed in mitmproxy 11.1.2 and above. ### Acknowledgements We thank Stefan Grönke (@gronke) for reporting this vulnerability as part of a security audit by [Radically Open Security](https://www.radicallyopensecurity.com/). This audit was supported by the [NGI0 Entrust fund](https://nlnet.nl/entrust/) established by [NLnet](https://nlnet.nl/). ### Timeline - **2025-01-14**: Received initial report. - **2025-01-14**: Verified report and confirmed receipt. - **2025-01-19**: Shared patch with researcher. - **2025-02-04**: Received final confirmation that patch is working. - **2025-02-05**: Published patched release and advisory.

Open Source Vulnerabilities CVE-2025-23217

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 mitmweb 11.1.1 and below, a malicious client can use mitmweb's proxy server (bound to `*:8080` by default) to access mitmweb's internal API (bound to `127.0.0.1:8081` by default). In other words, while the cannot access the API directly, they can access the API through the proxy. An attacker may be able to escalate this SSRF-style access to remote code execution. The mitmproxy and mitmdump tools are unaffected. Only mitmweb is affected. This vulnerability has been fixed in mitmproxy 11.1.2 and above. Users are advised to upgrade. There are no known workarounds for this vulnerability.