CVE-2018-1000807 is a high-severity (CVSS 8.1) Use After Free vulnerability in pyopenssl. A fix is available for pyopenssl — see the affected versions and patch details below.
PyOpenSSL Use-After-Free vulnerability
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-2018-1000807 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 378,567 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
pyopensslReal-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
Python Cryptographic Authority pyopenssl version prior to version 17.5.0 contains a CWE-416: Use After Free vulnerability in X509 object handling that can result in Use after free can lead to possible denial of service or remote code execution.. This attack appear to be exploitable via Depends on the calling application and if it retains a reference to the memory.. This vulnerability appears to have been fixed in 17.5.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyopenssl | all versions | 17.5.0pip install --upgrade 'pyopenssl==17.5.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyopenssl, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyopenssl to 17.5.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2018-1000807 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-2018-1000807 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2018-1000807. 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.
This vulnerability is only present when a specific and uncommon usage pattern of pyOpenSSL occurs. Red Hat Product Security has audited our packages that use pyOpenSSL, and determined that software we distribute in Red Hat Enterprise Linux and Red Hat Virtualization does not use pyOpenSSL in such a way as to be…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenStack Platform 13.0 (Queens) | pyOpenSSL-0:17.5.0-1.el7ost | RHSA-2019:0085 |
Frequently Asked Questions
Is CVE-2018-1000807 in your dependencies?
O3 Security finds CVE-2018-1000807 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.