CVE-2017-11173
HIGHCVE-2017-11173 is a high-severity (CVSS 8.8) vulnerability in rack-cors. O3 Security confirms whether CVE-2017-11173 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Missing Regex anchor in Rack-Cors allows malicious third party site to perform CORS request
Blast Radius
rack-corsReal-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
Missing anchor in generated regex for rack-cors before 0.4.1 allows a malicious third-party site to perform CORS requests. If the configuration were intended to allow only the trusted example.com domain name and not the malicious example.net domain name, then example.com.example.net (as well as example.com-example.net) would be inadvertently allowed.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rack-cors | all versions | 0.4.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack-cors. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update rack-cors to 0.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-11173 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 pinpoints whether CVE-2017-11173 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2017-11173. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2017-11173 in your dependencies?
O3 detects CVE-2017-11173 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.