CVE-2022-31183 is a critical-severity (CVSS 9.1) CWE-295 vulnerability in co.fs2:fs2-io. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2022-31183 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
mTLS client verification is skipped in fs2 on Node.js
Real-World Exposure
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
fs2 is a compositional, streaming I/O library for Scala. 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: 1. fs2-io running on Node.js. The JVM TLS implementation is completely independent. 2. TLSSockets in server-mode. Client-mode TLSSockets are implemented via a different API. 3. mTLS as enabled via requestCert = true in TLSParameters. The default setting is false for server-mode TLSSockets. It was introduced with the initial Node.js implementation of fs2-io in 3.1.0. 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. If using an unpatched version on Node.js, do not use a server-mode TLSSocket with requestCert = true to establish a mTLS connection.
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 CVE-2022-31183 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-2022-31183 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-2022-31183. 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-2022-31183 in your dependencies?
O3 detects CVE-2022-31183 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.