Netty up to 4.2.17.Final HTTP 3 Codec denial of service

Summaryinfo

A vulnerability labeled as problematic has been found in Netty up to 4.2.17.Final. Affected by this issue is some unknown functionality of the component HTTP 3 Codec. Executing a manipulation can lead to denial of service. This vulnerability is handled as CVE-2026-100660. The attack can be executed remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Netty up to 4.2.17.Final. It has been declared as problematic. This vulnerability affects an unknown part of the component HTTP 3 Codec. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. CVE summarizes:

Netty's HTTP/3 codec (io.netty:netty-codec-http3) from 4.2.0.Final through 4.2.17.Final retains unbounded per-stream QPACK encoder state. QpackEncoder stores a queue and a dynamic-table index tracker for every encoded field section that references the QPACK dynamic table, keyed by the peer-controlled QUIC stream ID, and these entries are released only when the remote decoder sends a Section Acknowledgment or Stream Cancellation instruction — not when the HTTP/3 stream completes. There is no limit on the number of tracked streams, field sections, or retained bytes. A remote, unauthenticated HTTP/3 client can advertise a non-zero QPACK dynamic-table capacity, acknowledge the table insertion so the server reuses a dynamically indexed response header, and then omit all mandatory Section Acknowledgments while issuing sequential requests over a single QUIC connection, bypassing concurrent-stream limits and causing unbounded heap growth until the server exhausts memory (denial of service). Fixed in 4.2.18.Final.

The advisory is available at github.com. This vulnerability was named CVE-2026-100660 since 09/26/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 4.2.18.Final eliminates this vulnerability.

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Productinfo

Name

• Netty

Version

• 4.2.17.Final

Website

• Product: https://github.com/netty/netty/

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