How severe is CVE-2026-45416?

CVE-2026-45416 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-45416?

CVE-2026-45416 affects the following packages: io.netty:netty-handler (Maven), io.netty:netty-handler (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-45416?

Update io.netty:netty-handler to 4.2.15.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45416 is resolved across your whole dependency graph.

How do I detect CVE-2026-45416 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-handler, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-45416 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-45416 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-45416 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-45416?

CVE-2026-45416 has an EPSS (Exploit Prediction Scoring System) score of 1.6%, placing it in the 74th 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.

What type of vulnerability is CVE-2026-45416?

CVE-2026-45416 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-45416 published, and has it been updated?

CVE-2026-45416 was published on June 12, 2026 and was last updated on September 20, 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

Not in CISA KEV

HIGH severity

CVE-2026-45416 — netty-handler

HIGH

CVE-2026-45416 is a high-severity (CVSS 7.5) CWE-770 vulnerability in io.netty:netty-handler. A fix is available for io.netty:netty-handler — see the affected versions and patch details below.

Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes

Also known asGHSA-x4gw-5cx5-pgmh

Published

Jun 12, 2026

Updated

Sep 20, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45416.

EPSS Exploitation Probability

via FIRST.org ↗

1.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs74th percentile — riskier than 74% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-45416 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

☕io.netty:netty-handler☕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 a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates ctx.alloc().buffer(handshakeLength) (line 161). The guard at line 140 is handshakeLength > maxClientHelloLength && maxClientHelloLength != 0, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.netty:netty-handler`	≥ 4.2.0.Final&&< 4.2.15.Final	4.2.15.Final`io.netty:netty-handler:4.2.15.Final`
☕Maven	`io.netty:netty-handler`	all versions	4.1.135.Final`io.netty:netty-handler:4.1.135.Final`

Affected Products

1 product · 2 configurations

Application

nettynetty

≥ 4.2.0 && < 4.2.15

range

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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-handler to 4.2.15.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45416 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This vulnerability in Netty is rated as Important. It allows a remote attacker to trigger a denial of service by sending a specially crafted TLS ClientHello message. The flaw arises from an eager, unbounded memory allocation during the TLS handshake, particularly when default configurations disable the maximum client…

Workaround published by Red Hat

To mitigate this issue, configure applications utilizing Netty's `SslClientHelloHandler` to specify a non-zero value for the `maxClientHelloLength` parameter. This will enable the internal length validation, preventing the eager allocation of large memory buffers when processing crafted TLS ClientHello messages. Refer to your specific application's documentation for details on configuring Netty's TLS handler. A restart of the affected application or service is required for the configuration changes to take effect.

Source: Red Hat security advisory for CVE-2026-45416 (CC BY 4.0)

Product	Fixed in	Advisory
AMQ Clients 2026.Q3	`netty-handler`	RHSA-2026:69459
Cryostat 4 on RHEL 9	`cryostat/cryostat-reports-rhel9:4.2.0-13`	RHSA-2026:48151
Red Hat AMQ Broker 7.13.6	`netty-handler`	RHSA-2026:66545
Red Hat AMQ Broker 7.14.1	`netty-handler`	RHSA-2026:66488
Red Hat Build of Apache Camel 3.33 for Quarkus 3.33.2.SP1	`netty-handler`	RHSA-2026:26586
Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16	`netty-handler`	RHSA-2026:37390
Red Hat build of Quarkus 3.27.4.SP1	`netty-handler`	RHSA-2026:26018
Red Hat build of Quarkus 3.33.2.SP1	`netty-handler`	RHSA-2026:26017

Frequently Asked Questions

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