Netty is a widely used Java networking library; an HTTP/3 QPACK DoS can disrupt many server applications and services across organizations.
CVE-2026-100662
HTTP/3 QPACK encoder allows remote OOM leading to DoS (Netty 4.2.0–4.2.17).
Is CVE-2026-100662 being exploited?
Not confirmed. CVE-2026-100662 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 0.34% probability of exploitation in the next 30 days.
How severe is CVE-2026-100662?
CVE-2026-100662 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-2026-100662?
Yes. A fix has been recorded for CVE-2026-100662. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-100662 affect?
CVE-2026-100662 affects io.netty:netty-codec-http3 4.2.0.Final - 4.2.17.Final, Netty-based HTTP/3 servers and services. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-100662?
Upgrade to netty-codec-http3 4.2.18.Final; limit QPACK/HTTP/3 stream sizes and monitor for OOMs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated attacker can force unbounded per-connection heap growth and trigger OutOfMemoryError, causing denial of service via crafted QPACK encoder-stream.
Patch when possible
- affected>= 4.2.0.Final and < 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.