FKIE_CVE-2026-72704

Vulnerability from fkie_nvd - Published: 2026-08-24 20:17 - Updated: 2026-10-12 15:10
Severity
6.3 (Medium) - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N
Summary
The guard checker in Rocq Prover does not recheck the recursive tree representation of an inductive type parameter after that parameter has been changed by transport. A fixpoint may apply a rewrite along an equality between types to its recursive argument, which the guard checker accepts because the inductive type is preserved, while the recursive tree recorded for the parameter is altered. A second fixpoint that calls the first inherits the altered recursive tree without verification, so a call that is not structurally decreasing is accepted as terminating. The resulting non-terminating definition proves that a natural number equals its own successor and therefore False, from which any proposition follows. The demonstration uses two axioms that follow from univalence and are consistent with the calculus of inductive constructions, so the contradiction comes from the guard check rather than from the assumptions. A fix is proposed but not merged.
References
disclosure@vulncheck.comhttps://github.com/endrazine/rocq-cve-poc-22024
disclosure@vulncheck.comhttps://github.com/rocq-prover/rocq
disclosure@vulncheck.comhttps://github.com/rocq-prover/rocq/issues/22024
disclosure@vulncheck.comhttps://github.com/rocq-prover/rocq/pull/22027
disclosure@vulncheck.comhttps://www.vulncheck.com/advisories/rocq-prover-through-guard-checker-trusts-corrupted-recursive-tree-after-transport
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:github/rocq-prover/rocq",
          "product": "rocq",
          "repo": "https://github.com/rocq-prover/rocq",
          "vendor": "rocq-prover",
          "versions": [
            {
              "lessThanOrEqual": "9.2.0",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "disclosure@vulncheck.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "The guard checker in Rocq Prover does not recheck the recursive tree representation of an inductive type parameter after that parameter has been changed by transport. A fixpoint may apply a rewrite along an equality between types to its recursive argument, which the guard checker accepts because the inductive type is preserved, while the recursive tree recorded for the parameter is altered. A second fixpoint that calls the first inherits the altered recursive tree without verification, so a call that is not structurally decreasing is accepted as terminating. The resulting non-terminating definition proves that a natural number equals its own successor and therefore False, from which any proposition follows. The demonstration uses two axioms that follow from univalence and are consistent with the calculus of inductive constructions, so the contradiction comes from the guard check rather than from the assumptions. A fix is proposed but not merged."
    },
    {
      "lang": "es",
      "value": "El verificador de guardas en Rocq Prover no vuelve a verificar la representaci\u00f3n en \u00e1rbol recursivo de un par\u00e1metro de tipo inductivo despu\u00e9s de que ese par\u00e1metro haya sido modificado por transporte. Un punto fijo puede aplicar una reescritura a lo largo de una igualdad entre tipos a su argumento recursivo, lo cual el verificador de guardas acepta porque el tipo inductivo se preserva, mientras que el \u00e1rbol recursivo registrado para el par\u00e1metro es alterado. Un segundo punto fijo que llama al primero hereda el \u00e1rbol recursivo alterado sin verificaci\u00f3n, por lo que una llamada que no es estructuralmente decreciente es aceptada como terminante. La definici\u00f3n no terminante resultante prueba que un n\u00famero natural es igual a su propio sucesor y por lo tanto Falso, de lo cual se sigue cualquier proposici\u00f3n. La demostraci\u00f3n utiliza dos axiomas que se derivan de la univalencia y son consistentes con el c\u00e1lculo de construcciones inductivas, por lo que la contradicci\u00f3n proviene del verificador de guardas en lugar de las suposiciones. Se propone una soluci\u00f3n pero no se ha fusionado."
    }
  ],
  "id": "CVE-2026-72704",
  "lastModified": "2026-10-12T15:10:00.207",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "NONE",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 4.0,
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "LOCAL",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.8,
          "baseSeverity": "MEDIUM",
          "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": "PASSIVE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/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": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-72704",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-25T16:37:22.786826Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-24T20:17:18.390",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/endrazine/rocq-cve-poc-22024"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/rocq-prover/rocq"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/rocq-prover/rocq/issues/22024"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/rocq-prover/rocq/pull/22027"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/rocq-prover-through-guard-checker-trusts-corrupted-recursive-tree-after-transport"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-670"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}



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