CVE-2024-1135 is a high-severity (CVSS 8.2) CWE-444 vulnerability in gunicorn. A fix is available for gunicorn — see the affected versions and patch details below.
Request smuggling leading to endpoint restriction bypass in Gunicorn
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 CVE-2024-1135.
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
CVE-2024-1135 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
gunicornReal-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
Gunicorn fails to properly validate Transfer-Encoding headers, leading to HTTP Request Smuggling (HRS) vulnerabilities. By crafting requests with conflicting Transfer-Encoding headers, attackers can bypass security restrictions and access restricted endpoints. This issue is due to Gunicorn's handling of Transfer-Encoding headers, where it incorrectly processes requests with multiple, conflicting Transfer-Encoding headers, treating them as chunked regardless of the final encoding specified. This vulnerability has been shown to allow access to endpoints restricted by gunicorn. This issue has been addressed in version 22.0.0.
To be affected users must have a network path which does not filter out invalid requests. These users are advised to block access to restricted endpoints via a firewall or other mechanism if they are unable to update.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | gunicorn | all versions | 22.0.0pip install --upgrade 'gunicorn==22.0.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for gunicorn, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update gunicorn to 22.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-1135 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 CVE-2024-1135 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2024-1135. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.4 for RHEL 8 | python3x-gunicorn-0:22.0.0-1.el8ap | RHSA-2024:3781 |
| Red Hat OpenShift Container Platform 4.12 | openshift4/ose-ironic-rhel9:v4.12.0-202406060836.p0.g9a3e609.assembly.stream.el9 | RHSA-2024:3713 |
| Red Hat OpenShift Container Platform 4.13 | openshift4/ose-ironic-rhel9:v4.13.0-202405072309.p0.g881e793.assembly.stream.el9 | RHSA-2024:2875 |
| Red Hat OpenShift Container Platform 4.14 | openshift4/ose-ironic-rhel9:v4.14.0-202405161337.p0.g62ee6d0.assembly.stream.el9 | RHSA-2024:3331 |
| Red Hat OpenShift Container Platform 4.15 | openshift4/ose-ironic-rhel9:v4.15.0-202405161507.p0.ge2415c8.assembly.stream.el9 | RHSA-2024:3327 |
| Red Hat OpenStack Platform 16.2 | python-gunicorn-0:19.9.0-11.el8ost | RHSA-2024:4054 |
| Red Hat OpenStack Platform 17.1 for RHEL 9 | python-gunicorn-0:20.0.4-7.el9ost | RHSA-2024:2727 |
| Red Hat Satellite 6.15 for RHEL 8 | python-gunicorn-0:22.0.0-1.el8pc | RHSA-2024:7987 |
Frequently Asked Questions
Is CVE-2024-1135 in your dependencies?
O3 Security finds CVE-2024-1135 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.