GHSA-gcx2-gvj7-pxv3 is a critical-severity (CVSS 9.8) CWE-444 vulnerability in mitmproxy. A fix is available for mitmproxy — see the affected versions and patch details below.
Insufficient Protection against HTTP Request Smuggling in mitmproxy
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-gcx2-gvj7-pxv3.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-gcx2-gvj7-pxv3 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
mitmproxyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
In mitmproxy 7.0.4 and below, a malicious client or server is able to perform HTTP request smuggling attacks through mitmproxy. This means that a malicious client/server could smuggle a request/response through mitmproxy as part of another request/response's HTTP message body. While mitmproxy would only see one request, the target server would see multiple requests. A smuggled request is still captured as part of another request's body, but it does not appear in the request list and does not go through the usual mitmproxy event hooks, where users may have implemented custom access control checks or input sanitization.
Unless you use mitmproxy to protect an HTTP/1 service, no action is required.
Patches
The vulnerability has been fixed in mitmproxy 8.0.0 and above.
Acknowledgements
We thank Zeyu Zhang (@zeyu2001) for responsibly disclosing this vulnerability to the mitmproxy team.
Timeline
- 2022-03-15: Received initial report.
- 2022-03-15: Verified report and confirmed receipt.
- 2022-03-16: Shared patch with researcher.
- 2022-03-16: Received confirmation that patch is working.
- 2022-03-19: Published patched release and advisory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | mitmproxy | all versions | 8.0.0pip install --upgrade 'mitmproxy==8.0.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mitmproxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mitmproxy to 8.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gcx2-gvj7-pxv3 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-gcx2-gvj7-pxv3 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-gcx2-gvj7-pxv3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-gcx2-gvj7-pxv3 in your dependencies?
O3 Security finds GHSA-gcx2-gvj7-pxv3 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.