CVE-2019-1020001 — yard
HIGHCVE-2019-1020001 is a high-severity (CVSS 7.5) Path Traversal vulnerability in yard. A fix is available for yard — see the affected versions and patch details below.
Path Traversal vulnerability that affects yard
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-2019-1020001 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 379,145 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
yardReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Possible arbitrary path traversal and file access via yard server
Impact
A path traversal vulnerability was discovered in YARD <= 0.9.19 when using yard server to serve documentation. This bug would allow unsanitized HTTP requests to access arbitrary files on the machine of a yard server host under certain conditions.
Thanks to CuongMX from Viettel Cyber Security for discovering this vulnerability.
Patches
Please upgrade to YARD v0.9.20 immediately if you are relying on yard server to host documentation in any untrusted environments.
Workarounds
For users who cannot upgrade, it is possible to perform path sanitization of HTTP requests at your webserver level. WEBrick, for example, can perform such sanitization by default (which you can use via yard server -s webrick), as can certain rules in your webserver configuration.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | yard | all versions | 0.9.20bundle update yard --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yard, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update yard to 0.9.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-1020001 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2019-1020001 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2019-1020001. 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.
Frequently Asked Questions
Is CVE-2019-1020001 in your dependencies?
O3 Security finds CVE-2019-1020001 across RubyGems dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.