CVE-2026-100655 netty CVE debrief

Who should care

Defenders and administrators responsible for Netty-based systems should assess exposure and apply patches or mitigations to prevent potential denial-of-service attacks. They should also review compensating controls for exposed systems while remediation is scheduled and verified, and check relevant monitoring, detection, and logs for exposed assets that need extra review.

Why it matters

CVE-2026-100655 is a denial-of-service vulnerability affecting Netty versions up to and including 4.1.137.Final and from 4.2.0.Final through 4.2.17.Final. Defenders should prioritize verifying exposure and applying patches or mitigations to prevent potential denial-of-service attacks.

• Potential denial-of-service attacks
• Unbounded heap and direct memory allocation
• JVM OutOfMemoryError and service crash

Technical summary

The vulnerability is caused by the SpdySessionHandler accepting an unlimited number of concurrent remote-initiated SPDY streams, which can lead to a JVM OutOfMemoryError and crash the service. The vulnerability affects Netty versions up to and including 4.1.137.Final and from 4.2.0.Final through 4.2.17.Final. A remote peer that opens a SPDY connection and sends millions of SYN_STREAM frames with FLAG_FIN=0 causes the server to allocate unbounded heap and direct memory, eventually triggering a JVM OutOfMemoryError and crashing the service.

Defensive priority

Defenders should prioritize verifying exposure and applying patches or mitigations to prevent potential denial-of-service attacks.

Recommended defensive actions

• Verify exposure by checking Netty versions and configurations
• Apply patches or mitigations to prevent potential denial-of-service attacks
• Monitor for potential attacks and anomalies
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its description, CVSS score, and affected versions. The vulnerability affects Netty versions up to and including 4.1.137.Final and from 4.2.0.Final through 4.2.17.Final. The SpdySessionHandler accepts an unlimited number of concurrent remote-initiated SPDY streams, which can lead to a JVM OutOfMemoryError and crash the service. The CVE record was published on 2026-09-26T14:16:48.243Z and has not been modified since then. The NVD detail

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.