High 7.5Published Sep 26, 2026

CVE-2026-100660Netty before 4.2.18.Final QpackEncoder Unbounded Memory Retention

Updated under an hour ago (2026-10-19 05:50 UTC)

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It affects netty. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.38%, higher than 29% of scored CVEs.

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Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.38% (percentile 29)
Assigned by: VulnCheck
NVD analysis: Deferred
Record last updated: Sep 28, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

netty netty netty:netty (from the name)	before 4.2.18.Final; 4.2.18.Final not affected	CNA record

References

https://github.com/netty/netty/security/advisories/GHSA-495p-pchh-r4mcvendor-advisory
https://www.vulncheck.com/advisories/netty-before-4.2.18-final-qpackencoder-unbounded-memory-retentionthird-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.