Zero-length HTTP/2 CONTINUATION frames bypass Mint's header-block byte-size cap and exhaust client memory

{
  "id": "6a26bf9024dea57188b4389a9dd8808abe84ef9a6a70fc2cd8aa2a3a0fe1859b",
  "url": "https://osv.dev/vulnerability/CVE-2026-59246",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Zero-length HTTP/2 CONTINUATION frames bypass Mint's header-block byte-size cap and exhaust client memory",
    "summary": "Allocation of resources without limits vulnerability in elixir-mint mint allows a remote HTTP/2 server to exhaust memory on the client host and cause a denial of service. The Mint.HTTP2.handle_continuation/3 function in lib/mint/http2.ex accumulates the header-block fragment carried by each HTTP/2 CONTINUATION frame into a growing conn.headers_being_processed nesting, one level deeper per frame, and only releases it when a frame with the END_HEADERS flag arrives. The only guard on this accumulator is Mint.HTTP2.assert_header_block_within_max_size/2, which sums the byte size of the fragments received so far. Because a CONTINUATION frame is permitted by the protocol to carry a zero-length payload, an unbounded chain of zero-length CONTINUATION frames adds no bytes to the running total, never trips the size cap, and never emits END_HEADERS, yet each frame still nests the accumulator one level deeper. A malicious HTTP/2 server (reachable directly, via an attacker-controlled redirect, via SSRF, or via a man-in-the-middle) can open a stream by sending a HEADERS frame without END_HEADERS and then stream zero-length CONTINUATION frames indefinitely. Client memory grows one cons cell per frame received; sustained bandwidth from the peer drives the BEAM node running the Mint client to memory exhaustion and eventual out-of-memory termination. This issue affects mint: from 0.1.0 before 1.9.2.",
    "evidence": "osv:CVE-2026-59246",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-59246",
      "aliases": [
        "CVE-2026-59246",
        "EEF-CVE-2026-59246",
        "GHSA-8pf6-g464-h6h9"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/elixir-mint/mint",
              "type": "GIT",
              "events": [
                {
                  "introduced": "596ca4304504be68939c4929e0831557097962b8"
                },
                {
                  "fixed": "5779de1666344b32aefc4354184ea07f902f73ce"
                },
                {
                  "introduced": "47889857fb36f07606ad9c2e52080d202d419058"
                },
                {
                  "fixed": "d066c6685dca58fceb2e22e97a9266866b622bfc"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "596ca4304504be68939c4929e0831557097962b8"
                      },
                      {
                        "fixed": "5779de1666344b32aefc4354184ea07f902f73ce"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0.1.0"
                      },
                      {
                        "fixed": "1.9.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "5779de1666344b32aefc4354184ea07f902f73ce"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v1.9.1",
            "v1.9.0",
            "v1.8.0",
            "v1.7.1",
            "v1.7.0",
            "v1.6.2",
            "v1.6.1",
            "v1.6.0",
            "v1.5.2",
            "v1.5.1",
            "v1.5.0",
            "v1.4.2",
            "v1.4.1",
            "v1.4.0",
            "v1.3.0",
            "v1.2.1",
            "v1.2.0",
            "v1.1.0",
            "v1.0.0",
            "v0.5.0",
            "v0.4.0",
            "v0.2.1",
            "v0.2.0",
            "v0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59246.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:47.768305940Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-59246.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-59246",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59246.json",
        "https://github.com/elixir-mint/mint/security/advisories/GHSA-8pf6-g464-h6h9",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-59246",
        "https://github.com/elixir-mint/mint/commit/5779de1666344b32aefc4354184ea07f902f73ce",
        "https://github.com/elixir-mint/mint"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "cna_assigner": "EEF",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59246.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-59246",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 515818,
  "published_at": "2026-07-14T08:37:04.609+00:00"
}