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HIGH severity

Missing Regex anchor in Rack-Cors allows malicious third party site to perform CORS requestGHSA-2j9c-9vmv-7m39

HIGHFix: cyu/rack-cors@42ebe6c

GHSA-2j9c-9vmv-7m39 is a high-severity (CVSS 8.8) vulnerability in rack-cors. A fix is available for rack-cors — see the affected versions and patch details below.

Also known asCVE-2017-11173
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs84th percentile — riskier than 84% of all scored CVEsHighest risk
1.25%1.78%2.31%2.84%1.8%2.3%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
💎rack-cors

Real-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

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsrack-corsall versions0.4.1bundle update rack-cors --conservative

Affected Products

2 products · 2 configurations
OS
debian linuxdebian
1 version
9.0
Application
rack-corsrack-cors_project
< 0.4.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack-cors, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update rack-cors to 0.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-2j9c-9vmv-7m39 is resolved across your whole dependency graph.

  3. 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.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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Missing Regex anchor in Rack-Cors allows malicious third…