Plug: multipart :length limit is not charged for part headers, enabling unbounded temp-file creation (denial of service)

{
  "id": "66fa7414e0b36669a3a64c7fa8cc942d26180b74b64273338ef43609c5c6ca05",
  "url": "https://osv.dev/vulnerability/CVE-2026-56814",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Plug: multipart :length limit is not charged for part headers, enabling unbounded temp-file creation (denial of service)",
    "summary": "Plug.Parsers.MULTIPART, the multipart request-body parser used to handle file uploads and multipart forms, does not enforce its :length budget against all consumed resources, allowing an unauthenticated remote attacker to cause denial of service. The parser charges the :length limit only for part body bytes; part header bytes are never counted, and a part with an empty body costs zero. Because every part whose Content-Disposition carries a non-empty filename creates a fresh temporary file (via Plug.Upload) and retains a Plug.Upload struct for the duration of the request, an attacker can send a single request composed of many empty-body file parts. Such a request stays well under the configured :length limit (8,000,000 bytes by default) while creating one temporary file per part, leading to inode and disk exhaustion and unbounded memory growth. Any application using Plug.Parsers with the :multipart parser is affected, and no authentication is required, only reachability of a multipart endpoint over HTTP. This vulnerability is associated with program files lib/plug/parsers/multipart.ex and program routines Plug.Parsers.MULTIPART.parse_multipart/2, Plug.Parsers.MULTIPART.parse_multipart_headers/5, Plug.Parsers.MULTIPART.parse_multipart_body/4, and Plug.Parsers.MULTIPART.parse_multipart_file/4. This issue affects plug: from 1.4.0-rc.0 before 1.16.6, from 1.17.0 before 1.17.4, from 1.18.0 before 1.18.5, from 1.19.1 before 1.19.5, and from 1.20.0 before 1.20.3.",
    "evidence": "osv:CVE-2026-56814",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-56814",
      "aliases": [
        "CVE-2026-56814",
        "EEF-CVE-2026-56814",
        "GHSA-95qv-c9g9-rm63"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/elixir-plug/plug",
              "type": "GIT",
              "events": [
                {
                  "introduced": "c52b2f32c90bccd718202bafccb5f95594e30183"
                },
                {
                  "fixed": "981597d3a4271ede64373c7a731702a42c500dd6"
                },
                {
                  "fixed": "c52b2f32c90bccd718202bafccb5f95594e30183"
                },
                {
                  "fixed": "56edca2ce35fe5589cd581644d8a4493fa5f484e"
                },
                {
                  "fixed": "0ee8afcc61466dc5f7a8f048d0632c899165b81f"
                },
                {
                  "fixed": "cae36053350e5215a4e0ca33cd130af9c5fc6364"
                },
                {
                  "fixed": "f7effaed811c00b5f5bf817936bfd9c5df27b7dc"
                },
                {
                  "fixed": "df97d3f17f808a9916a7700a701fb85314559d56"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "c52b2f32c90bccd718202bafccb5f95594e30183"
                      },
                      {
                        "fixed": "981597d3a4271ede64373c7a731702a42c500dd6"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "ChangesAt"
                  },
                  {
                    "range": [
                      {
                        "fixed": "c52b2f32c90bccd718202bafccb5f95594e30183"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "981597d3a4271ede64373c7a731702a42c500dd6"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "56edca2ce35fe5589cd581644d8a4493fa5f484e"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0ee8afcc61466dc5f7a8f048d0632c899165b81f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "cae36053350e5215a4e0ca33cd130af9c5fc6364"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f7effaed811c00b5f5bf817936bfd9c5df27b7dc"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "df97d3f17f808a9916a7700a701fb85314559d56"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-56814.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.473711724Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-56814.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-56814",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56814.json",
        "https://github.com/elixir-plug/plug/security/advisories/GHSA-95qv-c9g9-rm63",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-56814",
        "https://github.com/elixir-plug/plug/commit/0ee8afcc61466dc5f7a8f048d0632c899165b81f",
        "https://github.com/elixir-plug/plug/commit/56edca2ce35fe5589cd581644d8a4493fa5f484e",
        "https://github.com/elixir-plug/plug/commit/981597d3a4271ede64373c7a731702a42c500dd6",
        "https://github.com/elixir-plug/plug/commit/c52b2f32c90bccd718202bafccb5f95594e30183",
        "https://github.com/elixir-plug/plug/commit/cae36053350e5215a4e0ca33cd130af9c5fc6364",
        "https://github.com/elixir-plug/plug/commit/df97d3f17f808a9916a7700a701fb85314559d56",
        "https://github.com/elixir-plug/plug/commit/f7effaed811c00b5f5bf817936bfd9c5df27b7dc",
        "https://github.com/elixir-plug/plug"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "cna_assigner": "EEF",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "1.4.0-rc.0"
                  },
                  {
                    "fixed": "1.16.6"
                  },
                  {
                    "introduced": "1.17.0"
                  },
                  {
                    "fixed": "1.17.4"
                  },
                  {
                    "introduced": "1.18.0"
                  },
                  {
                    "fixed": "1.18.5"
                  },
                  {
                    "introduced": "1.19.1"
                  },
                  {
                    "fixed": "1.19.5"
                  },
                  {
                    "introduced": "1.20.0"
                  },
                  {
                    "fixed": "1.20.3"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/56xxx/CVE-2026-56814.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-56814",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492142,
  "published_at": "2026-07-10T11:14:35.574+00:00"
}