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.
Blast Radius
co.fs2:fs2-io☕co.fs2:fs2-io_2.12☕co.fs2:fs2-io_3☕co.fs2:fs2-io_2.13☕co.fs2:fs2-io_sjs1_2.13☕co.fs2:fs2-io_sjs1_3Real-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 server-mode TLSSocket using fs2-io on Node.js, the parameter requestCert = true is ignored, peer certificate verification is skipped, and the connection proceeds.
The vulnerability is limited to:
fs2-iorunning on Node.js. The JVM TLS implementation is completely independent.TLSSockets in server-mode. Client-modeTLSSockets are implemented via a different API.- mTLS as enabled via
requestCert = trueinTLSParameters. The default setting isfalsefor server-modeTLSSockets.
It was introduced with the initial Node.js implementation of fs2-io in v3.1.0.
Patches
A patch is released in v3.2.11. The requestCert = true parameter is respected and the peer certificate is verified. If verification fails, a SSLException is raised.
Workarounds
If using an unpatched version on Node.js, do not use a server-mode TLSSocket with requestCert = true to establish a mTLS connection.
References
- https://github.com/nodejs/node/issues/43994
- https://www.cloudflare.com/learning/access-management/what-is-mutual-tls/
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 | ≥ 3.1.0&&< 3.2.11 | 3.2.11 |
| ☕Maven | co.fs2:fs2-io_2.12 | ≥ 3.1.0&&< 3.2.11 | 3.2.11 |
| ☕Maven | co.fs2:fs2-io_3 | ≥ 3.1.0&&< 3.2.11 | 3.2.11 |
| ☕Maven | co.fs2:fs2-io_2.13 | ≥ 3.1.0&&< 3.2.11 | 3.2.11 |
| ☕Maven | co.fs2:fs2-io_sjs1_2.13 | ≥ 3.1.0&&< 3.2.11 | 3.2.11 |
| ☕Maven | co.fs2:fs2-io_sjs1_3 | ≥ 3.1.0&&< 3.2.11 | 3.2.11 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
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. 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 to 3.2.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-2cpx-6pqp-wf35 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-2cpx-6pqp-wf35 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-2cpx-6pqp-wf35. 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-2cpx-6pqp-wf35 in your dependencies?
O3 detects GHSA-2cpx-6pqp-wf35 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.