Resource exhaustion in Netty
CVE-2026-100658
Netty (io.netty:netty-codec-http) contains an unbounded per-connection queue in WebSocketServerExtensionHandler. The handler offers an entry to its per-channel validExtensions queue for every inbound HttpRequest, but polls an entry only when the application writes an HttpResponse, and the queue size is never bounded. A remote, unauthenticated peer can use HTTP/1.1 pipelining to send requests faster than the application produces responses — including plain non-upgrade HTTP requests to any path — causing the queue to grow without limit until the JVM exhausts heap memory and terminates with OutOfMemoryError. Because the affected handler is the base class of WebSocketServerCompressionHandler, any server that enables permessage-deflate is exposed on its plain HTTP port before any WebSocket upgrade completes and before any application-level authentication. Affected versions are 4.1.88.Final through 4.1.137.Final and 4.2.0.Final through 4.2.17.Final; the issue is fixed in 4.1.138.Final and 4.2.18.Final.
Published .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/netty/netty/security/advisories/GHSA-2g37-3h88-55hc (vendor-advisory)
- www.vulncheck.com/advisories/netty-before-4.1.138-final-denial-of-service-via-w… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-100658?
- CVE-2026-100658 is a medium-severity vulnerability in Netty, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-09-26.
- How severe is CVE-2026-100658?
- Medium severity. CVSS v3 base score is 5.3 out of 10.