CVE-2026-104635 (GCVE-0-2026-104635)

Vulnerability from cvelistv5 – Published: 2026-10-09 08:17 – Updated: 2026-10-09 09:24
VLAI
Title
Uncontrolled recursion in elixir-protobuf/protobuf JSON decoding of self-referential messages
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.
CWE
Assigner
EEF CNA under the mitre root
CNA scorecard A 96/100 over 297 records in the last 180 days details
Impacted products
Vendor Product Version CPE status
elixir-protobuf protobuf Affected: 0.8.0 , < 0.17.1 (semver)
    cpe:2.3:a:elixir-protobuf:protobuf:*:*:*:*:*:*:*:*
Create a notification for this product.
elixir-protobuf protobuf Affected: b0a1d4eaffaf50012fa71a8e931a47cf252d0370 , < e9432ad1c4099511905353cebcececa3a1f7c3ff (git)
    cpe:2.3:a:elixir-protobuf:protobuf:*:*:*:*:*:*:*:*
Create a notification for this product.
Date Public
2026-10-09 08:17
Show details on NVD website

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      "dateAssigned": "2026-10-08T15:40:42.000Z",
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      "title": "Uncontrolled recursion in elixir-protobuf/protobuf JSON decoding of self-referential messages",
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              "value": "\u003cp\u003eReject JSON documents whose nesting depth exceeds a fixed bound at the web or middleware layer before passing them to the decoder. No decoder option limits recursion for user-defined message types, so the check must happen before \u003ccode\u003eProtobuf.JSON.decode/3\u003c/code\u003e, \u003ccode\u003eProtobuf.JSON.decode!/3\u003c/code\u003e, or \u003ccode\u003eProtobuf.JSON.from_decoded/3\u003c/code\u003e is called.\u003c/p\u003e"
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              "value": "Reject JSON documents whose nesting depth exceeds a fixed bound at the web or middleware layer before passing them to the decoder. No decoder option limits recursion for user-defined message types, so the check must happen before `Protobuf.JSON.decode/3`, `Protobuf.JSON.decode!/3`, or `Protobuf.JSON.from_decoded/3` is called."
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              "value": "\u003col\u003e\n\u003cli\u003eDefine and compile a self-referential proto3 message, for example a \u003ccode\u003eTreeNode\u003c/code\u003e message with a single embedded field \u003ccode\u003echild\u003c/code\u003e of type \u003ccode\u003eTreeNode\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eBuild a JSON document that nests the \u003ccode\u003echild\u003c/code\u003e field several thousand levels deep, for example by wrapping \u003ccode\u003e{}\u003c/code\u003e in \u003ccode\u003e{\"child\": ...}\u003c/code\u003e 5,000 times.\u003c/li\u003e\n\u003cli\u003eDecode it with \u003ccode\u003eProtobuf.JSON.decode(json, TreeNode, recursion_limit: 100)\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eObserve that no \u003ccode\u003eProtobuf.JSON.DecodeError\u003c/code\u003e for an exceeded recursion limit is raised and the decoder walks every level. The same depth in a \u003ccode\u003eGoogle.Protobuf.Struct\u003c/code\u003e payload raises \u003ccode\u003e{:recursion_limit_exceeded, 100}\u003c/code\u003e. At larger depths the decoding process consumes hundreds of megabytes and crashes with stack and heap exhaustion.\u003c/li\u003e\n\u003c/ol\u003e"
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              "value": "1. Define and compile a self-referential proto3 message, for example a `TreeNode` message with a single embedded field `child` of type `TreeNode`.\n2. Build a JSON document that nests the `child` field several thousand levels deep, for example by wrapping `{}` in `{\"child\": ...}` 5,000 times.\n3. Decode it with `Protobuf.JSON.decode(json, TreeNode, recursion_limit: 100)`.\n4. Observe that no `Protobuf.JSON.DecodeError` for an exceeded recursion limit is raised and the decoder walks every level. The same depth in a `Google.Protobuf.Struct` payload raises `{:recursion_limit_exceeded, 100}`. At larger depths the decoding process consumes hundreds of megabytes and crashes with stack and heap exhaustion."
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          "value": "* Define and compile a self-referential proto3 message, for example a TreeNode message with a single embedded field child of type TreeNode.\n* Build a JSON document that nests the child field several thousand levels deep, for example by wrapping {} in {\"child\": ...} 5,000 times.\n* Decode it with Protobuf.JSON.decode(json, TreeNode, recursion_limit: 100).\n* Observe that no Protobuf.JSON.DecodeError for an exceeded recursion limit is raised and the decoder walks every level. The same depth in a Google.Protobuf.Struct payload raises {:recursion_limit_exceeded, 100}. At larger depths the decoding process consumes hundreds of megabytes and crashes with stack and heap exhaustion."
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              "value": "\u003cp\u003e\u003cstrong\u003e1. Entry points.\u003c/strong\u003e \u003ccode\u003eProtobuf.JSON.decode/3\u003c/code\u003e, \u003ccode\u003eProtobuf.JSON.decode!/3\u003c/code\u003e, and \u003ccode\u003eProtobuf.JSON.from_decoded/3\u003c/code\u003e in \u003ccode\u003elib/protobuf/json.ex\u003c/code\u003e validate options and call \u003ccode\u003eProtobuf.JSON.Decode.from_json_data/3\u003c/code\u003e, which builds a \u003ccode\u003estate\u003c/code\u003e map carrying \u003ccode\u003edepth: 0\u003c/code\u003e and the \u003ccode\u003erecursion_limit\u003c/code\u003e (default 100). \u003ccode\u003efrom_decoded/3\u003c/code\u003e accepts already-parsed data, so the underlying JSON parser never bounds the depth either.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Unguarded recursion.\u003c/strong\u003e For a user-defined message module, \u003ccode\u003einternal_from_json_data/3\u003c/code\u003e calls \u003ccode\u003edecode_message/4\u003c/code\u003e, which calls \u003ccode\u003edecode_regular_fields/3\u003c/code\u003e and \u003ccode\u003edecode_oneof_fields/3\u003c/code\u003e. Each field value passes through \u003ccode\u003edecode_value/3\u003c/code\u003e and, for a singular embedded message, reaches the \u003ccode\u003edecode_singular/3\u003c/code\u003e clause matching \u003ccode\u003eembedded?: true\u003c/code\u003e. That clause calls \u003ccode\u003einternal_from_json_data/3\u003c/code\u003e with \u003ccode\u003estate\u003c/code\u003e unchanged, so \u003ccode\u003estate.depth\u003c/code\u003e stays at 0 at every nesting level. Repeated fields and map values reach the same clause through \u003ccode\u003edecode_repeated/3\u003c/code\u003e and \u003ccode\u003edecode_map/3\u003c/code\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Guard coverage.\u003c/strong\u003e \u003ccode\u003eincrease_depth_and_maybe_throw/1\u003c/code\u003e increments \u003ccode\u003edepth\u003c/code\u003e and throws \u003ccode\u003e{:recursion_limit_exceeded, limit}\u003c/code\u003e when it exceeds the limit. It is called only from the \u003ccode\u003eGoogle.Protobuf.ListValue\u003c/code\u003e and \u003ccode\u003eGoogle.Protobuf.Struct\u003c/code\u003e clauses, which the \u003ccode\u003eGoogle.Protobuf.Value\u003c/code\u003e clause delegates to. The \u003ccode\u003erecursion_limit\u003c/code\u003e documentation scopes the option to those wrappers, and no other path checks depth.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4. Result.\u003c/strong\u003e A self-referential schema such as a \u003ccode\u003eTree\u003c/code\u003e message with a \u003ccode\u003eTree child\u003c/code\u003e field recurses once per JSON nesting level with no bound. Each level holds a live stack frame and allocates heap objects, so a sufficiently deep document exhausts the memory of the decoding process and crashes it. The BEAM \u003ccode\u003emax_heap_size\u003c/code\u003e process flag defaults to unlimited, so repeated or concurrent requests can exhaust the memory of the whole node.\u003c/p\u003e"
            },
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              "base64": false,
              "type": "text/markdown",
              "value": "**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 either.\n\n**2. Unguarded recursion.** For a user-defined message module, `internal_from_json_data/3` calls `decode_message/4`, which calls `decode_regular_fields/3` and `decode_oneof_fields/3`. Each field value passes through `decode_value/3` and, for a singular embedded message, reaches the `decode_singular/3` clause matching `embedded?: true`. That clause calls `internal_from_json_data/3` with `state` unchanged, so `state.depth` stays at 0 at every nesting level. Repeated fields and map values reach the same clause through `decode_repeated/3` and `decode_map/3`.\n\n**3. Guard coverage.** `increase_depth_and_maybe_throw/1` increments `depth` and throws `{:recursion_limit_exceeded, limit}` when it exceeds the limit. It is called only from the `Google.Protobuf.ListValue` and `Google.Protobuf.Struct` clauses, which the `Google.Protobuf.Value` clause delegates to. The `recursion_limit` documentation scopes the option to those wrappers, and no other path checks depth.\n\n**4. Result.** A self-referential schema such as a `Tree` message with a `Tree child` field recurses once per JSON nesting level with no bound. Each level holds a live stack frame and allocates heap objects, so a sufficiently deep document exhausts the memory of the decoding process and crashes it. The BEAM `max_heap_size` process flag defaults to unlimited, so repeated or concurrent requests can exhaust the memory of the whole node."
            }
          ],
          "value": "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 either.\n\n2. Unguarded recursion. For a user-defined message module, internal_from_json_data/3 calls decode_message/4, which calls decode_regular_fields/3 and decode_oneof_fields/3. Each field value passes through decode_value/3 and, for a singular embedded message, reaches the decode_singular/3 clause matching embedded?: true. That clause calls internal_from_json_data/3 with state unchanged, so state.depth stays at 0 at every nesting level. Repeated fields and map values reach the same clause through decode_repeated/3 and decode_map/3.\n\n3. Guard coverage. increase_depth_and_maybe_throw/1 increments depth and throws {:recursion_limit_exceeded, limit} when it exceeds the limit. It is called only from the Google.Protobuf.ListValue and Google.Protobuf.Struct clauses, which the Google.Protobuf.Value clause delegates to. The recursion_limit documentation scopes the option to those wrappers, and no other path checks depth.\n\n4. Result. A self-referential schema such as a Tree message with a Tree child field recurses once per JSON nesting level with no bound. Each level holds a live stack frame and allocates heap objects, so a sufficiently deep document exhausts the memory of the decoding process and crashes it. The BEAM max_heap_size process flag defaults to unlimited, so repeated or concurrent requests can exhaust the memory of the whole node."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
    "assignerShortName": "EEF",
    "cveId": "CVE-2026-104635",
    "datePublished": "2026-10-09T08:17:52.372Z",
    "dateReserved": "2026-10-08T14:45:01.406Z",
    "dateUpdated": "2026-10-09T09:24:37.025Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://repo.hex.pm",
                "cpes": [
                  "cpe:2.3:a:elixir-protobuf:protobuf:*:*:*:*:*:*:*:*"
                ],
                "defaultStatus": "unaffected",
                "modules": [
                  "\u0027Elixir.Protobuf.JSON.Decode\u0027",
                  "\u0027Elixir.Protobuf.JSON\u0027"
                ],
                "packageName": "protobuf",
                "packageURL": "pkg:hex/protobuf",
                "product": "protobuf",
                "programFiles": [
                  "lib/protobuf/json/decode.ex",
                  "lib/protobuf/json.ex"
                ],
                "programRoutines": [
                  {
                    "name": "\u0027Elixir.Protobuf.JSON.Decode\u0027:from_json_data/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON.Decode\u0027:decode_singular/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON\u0027:decode/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON\u0027:decode!/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON\u0027:from_decoded/3"
                  }
                ],
                "repo": "https://github.com/elixir-protobuf/protobuf",
                "vendor": "elixir-protobuf",
                "versions": [
                  {
                    "lessThan": "0.17.1",
                    "status": "affected",
                    "version": "0.8.0",
                    "versionType": "semver"
                  }
                ]
              },
              {
                "collectionURL": "https://github.com",
                "cpes": [
                  "cpe:2.3:a:elixir-protobuf:protobuf:*:*:*:*:*:*:*:*"
                ],
                "defaultStatus": "unaffected",
                "modules": [
                  "\u0027Elixir.Protobuf.JSON.Decode\u0027",
                  "\u0027Elixir.Protobuf.JSON\u0027"
                ],
                "packageName": "elixir-protobuf/protobuf",
                "packageURL": "pkg:github/elixir-protobuf/protobuf",
                "product": "protobuf",
                "programFiles": [
                  "lib/protobuf/json/decode.ex",
                  "lib/protobuf/json.ex"
                ],
                "programRoutines": [
                  {
                    "name": "\u0027Elixir.Protobuf.JSON.Decode\u0027:from_json_data/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON.Decode\u0027:decode_singular/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON\u0027:decode/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON\u0027:decode!/3"
                  },
                  {
                    "name": "\u0027Elixir.Protobuf.JSON\u0027:from_decoded/3"
                  }
                ],
                "repo": "https://github.com/elixir-protobuf/protobuf",
                "vendor": "elixir-protobuf",
                "versions": [
                  {
                    "lessThan": "e9432ad1c4099511905353cebcececa3a1f7c3ff",
                    "status": "affected",
                    "version": "b0a1d4eaffaf50012fa71a8e931a47cf252d0370",
                    "versionType": "git"
                  }
                ]
              }
            ],
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "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.\n\nIn 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\u0027s 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.\n\nThis issue affects protobuf: from 0.8.0 before 0.17.1."
          }
        ],
        "id": "CVE-2026-104635",
        "lastModified": "2026-10-09T10:16:37.143",
        "metrics": {
          "cvssMetricV40": [
            {
              "cvssData": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "LOW",
                "attackRequirements": "PRESENT",
                "attackVector": "NETWORK",
                "availabilityRequirement": "NOT_DEFINED",
                "baseScore": 8.2,
                "baseSeverity": "HIGH",
                "confidentialityRequirement": "NOT_DEFINED",
                "exploitMaturity": "NOT_DEFINED",
                "integrityRequirement": "NOT_DEFINED",
                "modifiedAttackComplexity": "NOT_DEFINED",
                "modifiedAttackRequirements": "NOT_DEFINED",
                "modifiedAttackVector": "NOT_DEFINED",
                "modifiedPrivilegesRequired": "NOT_DEFINED",
                "modifiedSubAvailabilityImpact": "NOT_DEFINED",
                "modifiedSubConfidentialityImpact": "NOT_DEFINED",
                "modifiedSubIntegrityImpact": "NOT_DEFINED",
                "modifiedUserInteraction": "NOT_DEFINED",
                "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
                "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
                "modifiedVulnIntegrityImpact": "NOT_DEFINED",
                "privilegesRequired": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "NONE",
                "vulnIntegrityImpact": "NONE",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-10-09T09:17:07.360",
        "references": [
          {
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "url": "https://cna.erlef.org/cves/CVE-2026-104635.html"
          },
          {
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "url": "https://github.com/elixir-protobuf/protobuf/commit/b0a1d4eaffaf50012fa71a8e931a47cf252d0370"
          },
          {
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "url": "https://github.com/elixir-protobuf/protobuf/commit/e9432ad1c4099511905353cebcececa3a1f7c3ff"
          },
          {
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "url": "https://github.com/elixir-protobuf/protobuf/security/advisories/GHSA-m497-c2h9-rvw6"
          },
          {
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "url": "https://osv.dev/vulnerability/EEF-CVE-2026-104635"
          }
        ],
        "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "vulnStatus": "Received",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-674"
              }
            ],
            "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-10-09T11:05:21+00:00",
      "cve": "CVE-2026-104635",
      "id": "CVE-2026-104635",
      "initial_release_date": "2026-10-09T08:17:52.372000+00:00",
      "product_status:known_affected": "46",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "protobuf: protobuf: Denial of Service via deeply nested JSON input",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-104635.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.


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