Resource exhaustion in Netty
CVE-2026-100660
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.
Published .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
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-495p-pchh-r4mc (vendor-advisory)
- www.vulncheck.com/advisories/netty-before-4.2.18-final-qpackencoder-unbounded-m… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-100660?
- CVE-2026-100660 is a high-severity vulnerability in Netty, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-09-26.
- How severe is CVE-2026-100660?
- High severity. CVSS v3 base score is 7.5 out of 10.