CVE-2024-1023 is a medium-severity (CVSS 6.5) CWE-401 vulnerability in io.vertx:vertx-core. O3 Security confirms whether CVE-2024-1023 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Io.vertx/vertx-core: memory leak due to the use of netty fastthreadlocal data structures in vertx
Real-World Exposure
io.vertx:vertx-core☕io.vertx:vertx-coreReal-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
A vulnerability in the Eclipse Vert.x toolkit results in a memory leak due to using Netty FastThreadLocal data structures. Specifically, when the Vert.x HTTP client establishes connections to different hosts, triggering the memory leak. The leak can be accelerated with intimate runtime knowledge, allowing an attacker to exploit this vulnerability. For instance, a server accepting arbitrary internet addresses could serve as an attack vector by connecting to these addresses, thereby accelerating the memory leak.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.vertx:vertx-core | ≥ 4.5.0&&< 4.5.2 | 4.5.2 |
| ☕Maven | io.vertx:vertx-core | ≥ 4.4.5&&< 4.4.7 | 4.4.7 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.vertx:vertx-core. 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 io.vertx:vertx-core to 4.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-1023 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-2024-1023 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-2024-1023. 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-2024-1023 in your dependencies?
O3 detects CVE-2024-1023 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.