Netty is widely used in Java servers/frameworks; this remote, unauthenticated HTTP/3 DoS can cause widespread service outages.
CVE-2026-100660
Netty HTTP/3 QPACK retains unbounded state, enabling remote OOM DoS.
Is CVE-2026-100660 being exploited?
Not confirmed. CVE-2026-100660 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.38% probability of exploitation in the next 30 days.
How severe is CVE-2026-100660?
CVE-2026-100660 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-100660?
Yes. A fix has been recorded for CVE-2026-100660. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-100660 affect?
CVE-2026-100660 affects io.netty:netty-codec-http3 4.2.0.Final - 4.2.17.Final, Applications/servers/proxies/frameworks using Netty HTTP/3 (QUIC). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-100660?
Upgrade to io.netty:netty-codec-http3 4.2.18.Final; throttle/monitor HTTP/3 connections.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated HTTP/3 client can cause unbounded heap growth by omitting QPACK Section Acknowledgments, leading to server OOM/denial of service.
Patch when possible
- affected< 4.2.18.Final
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.