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HIGH severity

CVE-2016-4970 — netty-handler

HIGHFix: netty/netty#5364

CVE-2016-4970 is a high-severity (CVSS 7.5) CWE-835 vulnerability in io.netty:netty-handler. EPSS puts its 30-day exploitation probability at 11.3% (96th percentile). A fix is available for io.netty:netty-handler — see the affected versions and patch details below.

Loop with Unreachable Exit Condition in Netty

Also known asGHSA-rv63-gqm8-9w8q
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
11.3%probability of exploitation in next 30 days
Moderate Risk0.00%
Lower risk than most CVEs96th percentile — riskier than 96% of all scored CVEsHighest risk
7.32%8.94%10.6%12.2%8.2%11.3%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

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

handler/ssl/OpenSslEngine.java in Netty 4.0.x before 4.0.37.Final and 4.1.x before 4.1.1.Final allows remote attackers to cause a denial of service (infinite loop).

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenio.netty:netty-handler≥ 4.0.0.Alpha1&&< 4.0.37.Final4.0.37.Finalio.netty:netty-handler:4.0.37.Final
☕Mavenio.netty:netty-handler≥ 4.1.0.Beta1&&< 4.1.1.Final4.1.1.Finalio.netty:netty-handler:4.1.1.Final

Affected Products

4 products · 5 configurations
Application
cassandraapache
1 version
3.11.4
Application
nettynetty
≥ 4.1.0 && < 4.1.1
range
Application
jboss data gridredhat
1 version
7.1
Application
jboss middleware text-only advisoriesredhat
1 version
1.0

Detection & mitigation playbook

Open-source dependency

  1. 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.

  2. Fix

    Update io.netty:netty-handler to 4.0.37.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2016-4970 is resolved across your whole dependency graph.

  3. 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 HatModerate
ProductFixed inAdvisory
Red Hat Fuse 7.7.0nettyRHSA-2020:3192
Red Hat JBoss A-MQ 6.3see advisoryRHSA-2017:0179
Red Hat JBoss Data Grid 7.1see advisoryRHSA-2017:1097

Frequently Asked Questions

handler/ssl/OpenSslEngine.java in Netty 4.0.x before 4.0.37.Final and 4.1.x before 4.1.1.Final allows remote attackers to cause a denial of service (infinite loop).
O3 Security · Impact-Aware SCA

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CVE-2016-4970: netty-handler DoS — Fixed in 4.0.37.Final