GHSA-v84h-653v-4pq9 is a critical-severity (CVSS 9.3) vulnerability in github.com/jub0bs/fcors. A fix is available for github.com/jub0bs/fcors — see the affected versions and patch details below.
Some CORS middleware allow untrusted origins
Real-World Exposure
github.com/jub0bs/fcorsReal-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
Impact
Some CORS middleware (more specifically those created by specifying two or more origin patterns whose hosts share a proper suffix) incorrectly allow some untrusted origins, thereby opening the door to cross-origin attacks from the untrusted origins in question.
For example, specifying origin patterns https://foo.com and https://bar.com (in that order) would yield a middleware that would incorrectly allow untrusted origin https://barfoo.com.
Patches
Patched in v0.9.0.
Workarounds
None.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/jub0bs/fcors | all versions | 0.9.0go get github.com/jub0bs/fcors@v0.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/jub0bs/fcors, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/jub0bs/fcors to 0.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v84h-653v-4pq9 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 GHSA-v84h-653v-4pq9 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-v84h-653v-4pq9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-v84h-653v-4pq9 in your dependencies?
O3 Security finds GHSA-v84h-653v-4pq9 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.