CVE-2025-58369
MEDIUMCVE-2025-58369 is a medium-severity (CVSS 5.3) Uncontrolled Resource Consumption vulnerability in co.fs2:fs2-io_2.12. O3 Security confirms whether CVE-2025-58369 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
fs2 is a compositional, streaming I/O library for Scala. Versions up to and including 2.5.12, 3.0.0-M1 through 3.12.2, and 3.13.0-M1 through 3.13.0-M6 are vulnerable to denial of service attacks though TLS sessions using fs2-io on the JVM using the fs2.io.net.tls package. When establishing a TLS session, 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. The CPU is consumed until the overall connection is closed, potentially shutting down a fs2-io powered server. This issue is fixed in versions 2.5.13, 3.12.1, and 3.13.0-M7.
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 CVE-2025-58369 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-2025-58369 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-2025-58369. 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-2025-58369 in your dependencies?
O3 detects CVE-2025-58369 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.