GHSA-rrw2-px9j-qffj
MEDIUMGHSA-rrw2-px9j-qffj is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in co.fs2:fs2-io_2.12. O3 Security confirms whether GHSA-rrw2-px9j-qffj is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
FS2 half-shutdown of socket during TLS handshake may result in spin loop on opposite side
Blast Radius
co.fs2:fs2-io_2.12☕co.fs2:fs2-io_2.12☕co.fs2:fs2-io_2.13☕co.fs2:fs2-io_2.13☕co.fs2:fs2-io_3☕co.fs2:fs2-io_3☕co.fs2:fs2-io_0.26☕co.fs2:fs2-io_0.27+9 moreReal-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
Impact
When establishing a TLS session using fs2-io on the JVM using the fs2.io.net.tls package, if one side of the connection shuts down write while the peer side is awaiting more data to progress the TLS handshake, the peer side will spin loop on the socket read, fully utilizing a CPU. This CPU is consumed until the overall connection is closed.
This could be used as a denial of service attack on an fs2-io powered server -- for example, by opening many connections and putting them in a half-shutdown state.
Note: this issue impacts ember backed http4s servers with HTTPS as a result of ember using fs2's TLS support.
Patches
Fixed in fs2 3.12.2 and 3.13.0-M7.
Workarounds
No workarounds.
For more information
If you have any questions or comments about this advisory:
Open an issue. Contact the Typelevel Security Team.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | co.fs2:fs2-io_2.12 | ≥ 3.0.0-M1&&< 3.12.2 | 3.12.2 |
| ☕Maven | co.fs2:fs2-io_2.12 | ≥ 3.13.0-M1&&< 3.13.0-M7 | 3.13.0-M7 |
| ☕Maven | co.fs2:fs2-io_2.13 | ≥ 3.0.0-M1&&< 3.12.2 | 3.12.2 |
| ☕Maven | co.fs2:fs2-io_2.13 | ≥ 3.13.0-M1&&< 3.13.0-M7 | 3.13.0-M7 |
| ☕Maven | co.fs2:fs2-io_3 | ≥ 3.0.0-M1&&< 3.12.2 | 3.12.2 |
| ☕Maven | co.fs2:fs2-io_3 | ≥ 3.13.0-M1&&< 3.13.0-M7 | 3.13.0-M7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for co.fs2:fs2-io_2.12. 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 co.fs2:fs2-io_2.12 to 3.12.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rrw2-px9j-qffj 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 GHSA-rrw2-px9j-qffj 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 GHSA-rrw2-px9j-qffj. 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-rrw2-px9j-qffj in your dependencies?
O3 detects GHSA-rrw2-px9j-qffj across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.