Uncontrolled recursion in elixir-protobuf/protobuf JSON decoding of self-referential messages

{
  "id": "fb390ce0c41c762e7649642accd6a0c8d23cf398e05663d063ab69399a3edcaa",
  "url": "https://osv.dev/vulnerability/EEF-CVE-2026-104635",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Uncontrolled recursion in elixir-protobuf/protobuf JSON decoding of self-referential messages",
    "summary": "## Summary Uncontrolled Recursion vulnerability in `Protobuf.JSON.Decode` in elixir-protobuf protobuf allows an unauthenticated remote attacker to crash the decoding process via a deeply nested JSON document. Any application that decodes attacker-supplied JSON with `Protobuf.JSON.decode/3`, `Protobuf.JSON.decode!/3`, or `Protobuf.JSON.from_decoded/3` into a schema that contains a self-referential or cyclic message type is affected. In `lib/protobuf/json/decode.ex`, the embedded-message clause of `decode_singular/3` recurses into `internal_from_json_data/3` once per nesting level without incrementing or checking the decoder's depth counter. The depth guard `increase_depth_and_maybe_throw/1` covers only the `Google.Protobuf.ListValue` and `Google.Protobuf.Struct` clauses, so the `recursion_limit` option has no effect on user-defined message types. Each nesting level allocates a stack frame and heap objects, and a sufficiently deep document exhausts the memory of the decoding process. Confidentiality and integrity are not affected. This issue affects protobuf: from 0.8.0 before 0.17.1. ## Details **1. Entry points.** `Protobuf.JSON.decode/3`, `Protobuf.JSON.decode!/3`, and `Protobuf.JSON.from_decoded/3` in `lib/protobuf/json.ex` validate options and call `Protobuf.JSON.Decode.from_json_data/3`, which builds a `state` map carrying `depth: 0` and the `recursion_limit` (default 100). `from_decoded/3` accepts already-parsed data, so the underlying JSON parser never bounds the depth ",
    "evidence": "osv:EEF-CVE-2026-104635",
    "products": [
      {
        "name": {
          "value": "protobuf",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.17.1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "0.10.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.11.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.12.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.13.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.14.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.14.1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.15.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.16.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.16.1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.17.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.8.0",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "0.9.0",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "high",
    "structured": {
      "id": "EEF-CVE-2026-104635",
      "aliases": [
        "CVE-2026-104635",
        "EEF-CVE-2026-104635",
        "GHSA-m497-c2h9-rvw6"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.8.0"
                },
                {
                  "fixed": "0.17.1"
                }
              ]
            }
          ],
          "package": {
            "name": "protobuf",
            "purl": "pkg:hex/protobuf",
            "ecosystem": "Hex"
          },
          "versions": [
            "0.10.0",
            "0.11.0",
            "0.12.0",
            "0.13.0",
            "0.14.0",
            "0.14.1",
            "0.15.0",
            "0.16.0",
            "0.16.1",
            "0.17.0",
            "0.8.0",
            "0.9.0"
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-104635.json"
          }
        },
        {
          "ranges": [
            {
              "repo": "https://github.com/elixir-protobuf/protobuf",
              "type": "GIT",
              "events": [
                {
                  "introduced": "b0a1d4eaffaf50012fa71a8e931a47cf252d0370"
                },
                {
                  "fixed": "e9432ad1c4099511905353cebcececa3a1f7c3ff"
                }
              ]
            }
          ],
          "versions": [
            "v0.17.0",
            "v0.16.0",
            "v0.15.0",
            "v0.14.1",
            "v0.14.0",
            "v0.13.0",
            "v0.12.0",
            "v0.11.0",
            "v0.10.0",
            "v0.9.0",
            "v0.8.0"
          ],
          "database_specific": {
            "source": "https://cna.erlef.org/osv/EEF-CVE-2026-104635.json"
          }
        }
      ],
      "modified": "2026-10-09T09:30:02.783183553Z",
      "provider": "osv",
      "references": [
        "https://github.com/elixir-protobuf/protobuf/security/advisories/GHSA-m497-c2h9-rvw6",
        "https://cna.erlef.org/cves/CVE-2026-104635.html",
        "https://github.com/elixir-protobuf/protobuf/commit/b0a1d4eaffaf50012fa71a8e931a47cf252d0370",
        "https://github.com/elixir-protobuf/protobuf/commit/e9432ad1c4099511905353cebcececa3a1f7c3ff",
        "https://hex.pm/packages/protobuf"
      ],
      "provider_metadata": {
        "cpe_ids": [
          "cpe:2.3:a:elixir-protobuf:protobuf:*:*:*:*:*:*:*:*"
        ],
        "cwe_ids": [
          "CWE-674"
        ],
        "capec_ids": [
          "CAPEC-230"
        ]
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-104635",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 111388,
  "published_at": "2026-10-09T08:17:52.372+00:00"
}