Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-100661",
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "dateUpdated": "2026-09-26T13:23:28.303Z",
    "dateReserved": "2026-09-26T02:33:59.039Z",
    "datePublished": "2026-09-26T13:23:28.303Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck",
        "dateUpdated": "2026-09-26T13:23:28.303Z"
      },
      "datePublic": "2026-09-10T00:00:00.000Z",
      "title": "Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation",
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "affected": [
        {
          "vendor": "netty",
          "product": "netty",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "4.2.0.Final",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.2.18.Final"
            },
            {
              "version": "4.2.18.Final",
              "status": "unaffected",
              "versionType": "semver"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "Uncontrolled Resource Consumption",
              "cweId": "CWE-400",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://github.com/netty/netty/security/advisories/GHSA-v5p2-hmgx-3xrx",
          "name": "GitHub Security Advisory (GHSA-v5p2-hmgx-3xrx)",
          "tags": [
            "vendor-advisory"
          ]
        },
        {
          "url": "https://www.vulncheck.com/advisories/netty-http-3-qpack-prefixed-integer-dos-via-unbounded-accumulation",
          "name": "VulnCheck Advisory: Netty HTTP/3 QPACK Prefixed Integer DoS via Unbounded Accumulation",
          "tags": [
            "third-party-advisory"
          ]
        }
      ],
      "metrics": [
        {
          "format": "CVSS"
        },
        {
          "format": "CVSS",
          "cvssV3_1": {
            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "attackVector": "NETWORK",
            "attackComplexity": "LOW",
            "privilegesRequired": "NONE",
            "userInteraction": "NONE",
            "scope": "UNCHANGED",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH"
          }
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "manus-use",
          "type": "reporter"
        }
      ]
    }
  }
}