CVE-2021-32643 is a medium-severity (CVSS 5.8) Path Traversal vulnerability in org.http4s:http4s-core. O3 Security confirms whether CVE-2021-32643 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
StaticFile.fromUrl can leak presence of a directory
Real-World Exposure
org.http4s:http4s-core☕org.http4s:http4s-core☕org.http4s:http4s-core☕org.http4s:http4s-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Http4s is a Scala interface for HTTP services. StaticFile.fromUrl can leak the presence of a directory on a server when the URL scheme is not file://, and the URL points to a fetchable resource under its scheme and authority. The function returns F[None], indicating no resource, if url.getFile is a directory, without first checking the scheme or authority of the URL. If a URL connection to the scheme and URL would return a stream, and the path in the URL exists as a directory on the server, the presence of the directory on the server could be inferred from the 404 response. The contents and other metadata about the directory are not exposed. This affects http4s versions: 0.21.7 through 0.21.23, 0.22.0-M1 through 0.22.0-M8, 0.23.0-M1, and 1.0.0-M1 through 1.0.0-M22. The patch is available in the following versions: v0.21.24, v0.22.0-M9, v0.23.0-M2, v1.0.0-M23. As a workaround users can avoid calling StaticFile.fromUrl with non-file URLs.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.http4s:http4s-core | ≥ 0.21.7&&< 0.21.24 | 0.21.24 |
| ☕Maven | org.http4s:http4s-core | ≥ 0.22.0-M1&&< 0.22.0-RC1 | 0.22.0-RC1 |
| ☕Maven | org.http4s:http4s-core | ≥ 0.23.0-M1&&< 0.23.0-RC1 | 0.23.0-RC1 |
| ☕Maven | org.http4s:http4s-core | ≥ 1.0.0-M1&&< 1.0.0-M23 | 1.0.0-M23 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-core. 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 org.http4s:http4s-core to 0.21.24 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32643 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-2021-32643 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-2021-32643. 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-2021-32643 in your dependencies?
O3 detects CVE-2021-32643 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.