How severe is CVE-2023-34462?

CVE-2023-34462 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-34462?

CVE-2023-34462 affects the following packages: io.netty:netty-handler (Maven). Ecosystems affected: Maven.

How do I fix CVE-2023-34462?

Update io.netty:netty-handler to 4.1.94.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-34462 is resolved across your whole dependency graph.

How do I detect CVE-2023-34462 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-handler. 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.

How do I mitigate CVE-2023-34462 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2023-34462?

O3 pinpoints whether CVE-2023-34462 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2023-34462 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2023-34462, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2023-34462?

CVE-2023-34462 has an EPSS (Exploit Prediction Scoring System) score of 2.5%, placing it in the 82th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2023-34462 published, and has it been updated?

CVE-2023-34462 was published on June 22, 2023 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

CVE-2023-34462

MEDIUM

netty-handler SniHandler 16MB allocation

Also known asGHSA-6mjq-h674-j845

Published

Jun 22, 2023

Updated

Apr 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

2.5%probability of exploitation in next 30 days

Lower Risk82th percentile+1.72%

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

1 pkg affected

☕io.netty:netty-handler

Real-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

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. The SniHandler can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the SniHandler to allocate 16MB of heap. The SniHandler class is a handler that waits for the TLS handshake to configure a SslHandler according to the indicated server name by the ClientHello record. For this matter it allocates a ByteBuf using the value defined in the ClientHello record. Normally the value of the packet should be smaller than the handshake packet but there are not checks done here and the way the code is written, it is possible to craft a packet that makes the SslClientHelloHandler. This vulnerability has been fixed in version 4.1.94.Final.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.netty:netty-handler`	all versions	4.1.94.Final

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Netty is an asynchronous event-driven network application framework for …

github.comNVDJun 2023

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-handler. 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.netty:netty-handler to 4.1.94.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-34462 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-2023-34462 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-2023-34462. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. The `SniHandler` can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the `SniHandler` to allocate 16MB of heap. The `SniHandler` class is a handler that waits for the TLS handshake to configure a `SslHandler` according to the indicated server name by the `ClientHello` record. For this matter it allocates a `ByteBuf` usi

O3 Security · Impact-Aware SCA

Is CVE-2023-34462 in your dependencies?

O3 detects CVE-2023-34462 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works