CVE-2020-12666
MEDIUMCVE-2020-12666 is a medium-severity (CVSS 6.1) Open Redirect vulnerability in gopkg.in/macaron.v1. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2020-12666 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
gopkg.in/macaron.v1 Open Redirect vulnerability
Real-World Exposure
gopkg.in/macaron.v1Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
macaron before 1.3.7 has an open redirect in the static handler, as demonstrated by the http://127.0.0.1:4000//example.com/ URL.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | gopkg.in/macaron.v1 | all versions | 1.3.7 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for gopkg.in/macaron.v1. 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 gopkg.in/macaron.v1 to 1.3.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-12666 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-2020-12666 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-2020-12666. 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 issue has a low impact on both OpenShift Container Platform and OpenShift Service Mesh grafana containers. As neither components make use of the Static handler the impact is Low. A future version of Grafana may use the Macaron Static handler so we may fix this in a future release. Red Hat Ceph Storage (RHCS)…
Frequently Asked Questions
Is CVE-2020-12666 in your dependencies?
O3 detects CVE-2020-12666 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.