{"cve":{"cve_id":"CVE-2026-100661","is_kev":false,"kev_date_added":null,"kev_vendor_project":null,"kev_product":null,"kev_vulnerability_name":null,"kev_short_description":null,"kev_required_action":null,"kev_due_date":null,"kev_known_ransomware":null,"kev_notes":null,"kev_cwes":null,"epss_score":0.00343,"epss_percentile":0.26231,"epss_as_of":"2026-10-15","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.","published_at":"2026-09-26T13:23:28.303000Z","last_modified_at":"2026-10-02T21:16:53.830000Z","cvss_v3_score":7.5,"cvss_v3_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cvss_v3_severity":"HIGH","cvss_v4_score":8.7,"cvss_v4_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","cvss_v4_severity":"HIGH","ssvc_decision":null,"ssvc_exploitation":null,"ssvc_automatable":null,"ssvc_technical_impact":null,"cwes":["CWE-400"],"nvd_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"],"vuln_status":"Deferred","trending_score":null,"is_trending":false,"has_trended":false,"trended_number_one":false,"trending_peak_score":null,"trending_peak_rank":null,"started_trending_at":null,"trended_number_one_at":null,"summary_generated":null,"summary_generated_at":null,"summary_model":null,"created_at":"2026-09-26T15:38:54.189773Z","updated_at":"2026-10-03T10:11:53.374013Z"},"effective_severity":"HIGH","badges":[],"impact_analysis":[],"cvss_v3_decoded":{"version":"3.1","metrics":[{"metric":"AV","name":"Attack Vector","value":"N","value_label":"Network"},{"metric":"AC","name":"Attack Complexity","value":"L","value_label":"Low"},{"metric":"PR","name":"Privileges Required","value":"N","value_label":"None"},{"metric":"UI","name":"User Interaction","value":"N","value_label":"None"},{"metric":"S","name":"Scope","value":"U","value_label":"Unchanged"},{"metric":"C","name":"Confidentiality","value":"N","value_label":"None"},{"metric":"I","name":"Integrity","value":"N","value_label":"None"},{"metric":"A","name":"Availability","value":"H","value_label":"High"}]},"cvss_v4_decoded":{"version":"4.0","metrics":[{"metric":"AV","name":"Attack Vector","value":"N","value_label":"Network"},{"metric":"AC","name":"Attack Complexity","value":"L","value_label":"Low"},{"metric":"AT","name":"Attack Requirements","value":"N","value_label":"None"},{"metric":"PR","name":"Privileges Required","value":"N","value_label":"None"},{"metric":"UI","name":"User Interaction","value":"N","value_label":"None"},{"metric":"VC","name":"Confidentiality (Vulnerable System)","value":"N","value_label":"None"},{"metric":"VI","name":"Integrity (Vulnerable System)","value":"N","value_label":"None"},{"metric":"VA","name":"Availability (Vulnerable System)","value":"H","value_label":"High"},{"metric":"SC","name":"Confidentiality (Subsequent System)","value":"N","value_label":"None"},{"metric":"SI","name":"Integrity (Subsequent System)","value":"N","value_label":"None"},{"metric":"SA","name":"Availability (Subsequent System)","value":"N","value_label":"None"}]},"affected":[{"vendor_slug":"netty","vendor_name":"netty","product_slug":"netty","product_name":"netty","version_start":"4.2.0.Final","version_start_inclusive":true,"version_end":"4.2.18.Final","version_end_inclusive":false,"cpe23_uri":"cve5:netty:netty:4.2.0.Final:4.2.18.Final"},{"vendor_slug":"netty","vendor_name":"netty","product_slug":"netty","product_name":"netty","version_start":"4.2.18.Final","version_start_inclusive":true,"version_end":"4.2.18.Final","version_end_inclusive":true,"cpe23_uri":"cve5:netty:netty:4.2.18.Final:4.2.18.Final"}],"exploit_refs":[],"news":[],"references":[{"url":"https://github.com/netty/netty/security/advisories/GHSA-v5p2-hmgx-3xrx","source_type":"VENDOR_ADVISORY","tags":["advisory"]},{"url":"https://www.vulncheck.com/advisories/netty-http-3-qpack-prefixed-integer-dos-via-unbounded-accumulation","source_type":"VENDOR_ADVISORY","tags":["advisory","patch"]}],"timeline":[{"type":"published","at":"2026-09-26T13:23:28.303000Z","label":"CVE published","source":null}]}