{"id":"CVE-2026-100661","revision":"c178fdbb47ca4abd810342d15906e6d9","records":[{"revision":"c178fdbb47ca4abd810342d15906e6d9","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-100661","aliases":[],"title":"Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation","description":"Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final contain a denial-of-service vulnerability in the QPACK prefixed-integer decoder (QpackUtil.decodePrefixedInteger), which does not bound the number of continuation bytes it will process. A remote, unauthenticated peer can open a QPACK unidirectional stream (type 0x02 encoder or 0x03 decoder) and send a first byte with all prefix bits set (e.g. 0xFF for a 7-bit prefix or 0x3F for a 5-bit prefix) followed by an endless run of 0x80 continuation bytes. The decoder returns -1 ('need more bytes'), so callers never consume the input, the ByteToMessageDecoder cumulator grows without bound, and each decode() invocation re-scans the whole accumulated buffer, yielding O(N^2) CPU cost. The result is unbounded per-connection heap growth (OutOfMemoryError) and event-loop CPU starvation, reachable in every configuration. Fixed in 4.2.18.Final.","state":0,"publishedAt":"2026-09-26T13:23:28.303+00:00","modifiedAt":"2026-10-02T20:46:26.627+00:00","affected":[{"ecosystem":"Vendor product","name":"netty","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"netty\",\n                    \"product\": \"netty\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"packageURL\": \"pkg:maven/io.netty/netty-codec-http3\",\n                    \"versions\": [\n                        {\n                            \"version\": \"4.2.0.Final\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"custom\",\n                            \"lessThan\": \"4.2.18.Final\"\n                        },\n                        {\n                            \"version\": \"4.2.18.Final\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"custom\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","score":8.7,"severity":"HIGH"},{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/netty/netty/security/advisories/GHSA-v5p2-hmgx-3xrx","https://www.vulncheck.com/advisories/netty-http-3-qpack-prefixed-integer-dos-via-unbounded-accumulation"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-100661","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-100661","identifiers":["CVE-2026-100661"]},"retained":false,"historicalAffected":[]}],"coverage":[]}