{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "4.2.0.Final"
              },
              {
                "fixed": "4.2.18.Final"
              },
              {
                "fixed": "4.2.17.Final"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "DESCRIPTION"
            ]
          },
          "events": [
            {
              "introduced": "09e64d259c99be8b5b2a471a78f11e65eb82598a"
            },
            {
              "fixed": "2521f494432e27415a567d3a81a9eb907abf20b3"
            }
          ],
          "repo": "https://github.com/netty/netty",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-v5p2-hmgx-3xrx"
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-400"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100661.json"
  },
  "details": "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.",
  "id": "CVE-2026-100661",
  "modified": "2026-09-30T03:31:00.824183422Z",
  "published": "2026-09-26T13:23:28.303Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100661.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/netty/netty/security/advisories/GHSA-v5p2-hmgx-3xrx"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-100661"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.vulncheck.com/advisories/netty-http-3-qpack-prefixed-integer-dos-via-unbounded-accumulation"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation"
}