Applications
CVE-2026-100660
Netty HTTP/3 QPACK retains unbounded state, enabling remote OOM DoS.
Major vulnerability. Netty is widely used in Java servers/frameworks; this remote, unauthenticated HTTP/3 DoS can cause widespread service outages.
- CVSS
- 8.7Highscored by the publisher (CNA)
- Exploited in the wild
- Not knownpublic proof of concept per CISA SSVC; not in CISA KEV
- EPSS
- 0.45%chance of exploitation in the next 30 daystop 61% of scored CVEsFIRST score of 12 Nov 2026
- Fix
- Fixed in 4.2.18.Finalper the vendor
- Published
- 26 Sept 2026analysed here 28 Sept 2026
Do first. Upgrade to a fixed release: 4.2.18.Final.
Summary
Impact
Remote unauthenticated HTTP/3 client can cause unbounded heap growth by omitting QPACK Section Acknowledgments, leading to server OOM/denial of service.
Triage
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| netty | < 4.2.18.FinalVendor says fixed in: 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.
Products named in our analysis
- io.netty:netty-codec-http3 4.2.0.Final - 4.2.17.Final
- Applications/servers/proxies/frameworks using Netty HTTP/3 (QUIC)
Fix and mitigation
Action required
Patch when possible
WAF and other mitigations
Can a WAF block it? No. The vulnerability is triggered by HTTP/3 requests that cause the server to retain unbounded state, leading to out-of-memory conditions. The malicious requests appear as normal HTTP/3 traffic, so a WAF cannot reliably distinguish them from legitimate requests.
Also consider: rate limit · patch
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Not listed as of our last sync.
- Public exploit code
- None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
- CISA SSVC
- exploitation poc, automatable yes, technical impact partialAssessed by CISA 28 Sept 2026 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Timeline
- 26 Sept 2026Published
- 28 Sept 2026Analysed by vulneraibility.com2 days later
- 28 Sept 2026CISA SSVC assessment: exploitation pocsame day later
- 28 Sept 2026CVE record last updatedsame day later
Common questions
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 0.45% 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.
References
2 references in the CVE record, grouped by the tags the record gives them.
Advisories (2)
- github.com /netty/netty/security/advisories/GHSA-495p-pchh-r4mc
- vulncheck.com /advisories/netty-before-4.2.18-final-qpackencoder-unbounded-memory-retention
Also tracked as GHSA-495p-pchh-r4mc (OSV).
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- OSV: advisory aliases and downstream package versions
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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