Summary
Acknowledgements
We thank Stefan Grönke (@gronke) for reporting this vulnerability as part of a security audit by Radically Open Security. This audit was supported by the NGI0 Entrust fund established by NLnet.
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.
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-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.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
The vulnerability has been fixed in mitmproxy 11.1.2 and above.
Frequently Asked Questions
- What is CVE-2025-23217? CVE-2025-23217 is a high-severity security vulnerability in mitmproxy (pip), affecting versions < 11.1.2. It is fixed in 11.1.2.
- Which versions of mitmproxy are affected by CVE-2025-23217? mitmproxy (pip) versions < 11.1.2 is affected.
- Is there a fix for CVE-2025-23217? Yes. CVE-2025-23217 is fixed in 11.1.2. Upgrade to this version or later.
- Is CVE-2025-23217 exploitable, and should I be worried? Whether CVE-2025-23217 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-23217 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-23217? Upgrade
mitmproxyto 11.1.2 or later.