GHSA-rrw2-px9j-qffj is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in co.fs2:fs2-io_2.12. A fix is available for co.fs2:fs2-io_2.12 — see the affected versions and patch details below.
FS2 half-shutdown of socket during TLS handshake may result in spin loop on opposite side
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-rrw2-px9j-qffj.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-rrw2-px9j-qffj plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 376,715 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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 | 3.12.2co.fs2:fs2-io_2.12:3.12.2 |
| ☕Maven | co.fs2:fs2-io_2.12 | ≥ 3.13.0-M1&&< 3.13.0-M7 | 3.13.0-M7co.fs2:fs2-io_2.12:3.13.0-M7 |
| ☕Maven | co.fs2:fs2-io_2.13 | ≥ 3.0.0-M1&&< 3.12.2 | 3.12.2co.fs2:fs2-io_2.13:3.12.2 |
| ☕Maven | co.fs2:fs2-io_2.13 | ≥ 3.13.0-M1&&< 3.13.0-M7 | 3.13.0-M7co.fs2:fs2-io_2.13:3.13.0-M7 |
| ☕Maven | co.fs2:fs2-io_3 | ≥ 3.0.0-M1&&< 3.12.2 | 3.12.2co.fs2:fs2-io_3:3.12.2 |
| ☕Maven | co.fs2:fs2-io_3 | ≥ 3.13.0-M1&&< 3.13.0-M7 | 3.13.0-M7co.fs2:fs2-io_3:3.13.0-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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-rrw2-px9j-qffj can be triaged on real exposure rather than presence alone.
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 Security finds GHSA-rrw2-px9j-qffj across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.