{
  "affected": [
    {
      "affectedData": [
        {
          "product": "klever-go",
          "vendor": "klever-io",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.7.20"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, the KleverUpdateAccountPermission built-in authorizes replacement of a target account\u0027s permissions by checking attacker-controlled vmInput.RecipientAddr instead of authenticated vmInput.CallerAddr. An attacker-controlled contract can choose a victim account with configured permissions as RecipientAddr, and contractHasValidPermission can accept the victim\u0027s default self-signer as authorization. UpdatePermission can then replace the victim\u0027s entire permission set with attacker-supplied Owner permissions, enabling asset theft or permanent lockout without a victim key or signature. Accounts without stored permissions and the native transaction path are not affected. This issue is fixed in version 1.7.20."
    }
  ],
  "id": "CVE-2026-82405",
  "lastModified": "2026-09-23T20:17:16.500",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.7,
          "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": "LOW",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/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": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-23T20:17:16.370",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://gist.github.com/mabdullah22/a41f90aa5ba86bbebf121f739bd5f5e9"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/klever-io/klever-go/commit/c58740eb74d7ee8f07db1e18a7d6214b5559ba32"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/klever-io/klever-go/releases/tag/v1.7.20"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/klever-io/klever-go/security/advisories/GHSA-97cv-x867-6xhm"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.7.19"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/klever-io/klever-go"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.7.20"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-82405"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-23T19:27:08Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Description\n\nThe VM built-in function `KleverUpdateAccountPermission` (registered always-active, `creator.go:381-390` / `core/vmconstants.go:234`) rewrites an account\u0027s entire permission set. Its authorization check uses `vmInput.RecipientAddr` **attacker-controlled**  instead of the authenticated `vmInput.CallerAddr`. The sibling handler `kleverChangeOwnerAddress.go:86` uses `vmInput.CallerAddr` correctly, so the safe pattern exists in-repo; this handler deviates. The native transaction path (`txProcess.go:833`) is safe  it uses `tx.GetSender()`.\n\nMechanism:\n1. **Wrong variable:** `CallerAddr` is never referenced in the handler; auth is `contractHasValidPermission(target.GetPermissions(), RecipientAddr)`, which returns true if `RecipientAddr` is a signer with `Weight \u003e= Threshold` in the *target* account\u0027s permissions and the permission grants `UpdateAccountPermissionContractType`.\n2. **RecipientAddr is attacker-controlled:** when a contract calls a built-in via `ExecuteOnDestContextWithTypedArgs` (`baseOps.go:1967`), `prepareIndirectContractCallInput` (`baseOps.go:2485`) sets `RecipientAddr = destination` (contract-chosen) and `CallerAddr = the calling contract`. The blockchain hook (`blockChainHook.go:454/467`) dispatches on `input.Function` and passes the input through unchanged; no guard forces `RecipientAddr == CallerAddr` and there is no SC-destination validation on this path.\n3. **Self-signer default satisfies the check:** `createDefaultOwnerPermission` (`accounts.go:1848`) makes an account its own signer (weight 1, threshold 1, Owner type), and `CheckPermissionGrantedForContracts` returns true for Owner, so `contractHasValidPermission(V.perms, V) == true`. (More generally, `RecipientAddr` can be set to *any* of V\u0027s signer addresses meeting threshold all public on-chain.) Accounts with no stored permissions have empty `GetPermissions()` and are immune.\n4. **Overwrite is unrestricted:** `UpdatePermission(V, attackerContract)` (`accounts.go:1863`) replaces V\u0027s permission set with attacker-supplied signers; if the attacker supplies an Owner-type permission, no default is appended and V\u0027s prior control is fully evicted.\n\n### Code walkthrough\n\n**(a) The vulnerable handler** \u2014 `core/kapp/builtInFunctions/kleverUpdateAccountPermission.go`:\n```go\nfunc (e *kleverUpdateAccountPermission) ProcessBuiltinFunction(vmInput *vmcommon.ContractCallInput) (*vmcommon.VMOutput, error) {\n    ...\n    address := vmInput.NextArg()                       // Arguments[0] \u2014 attacker-chosen target account V\n    contract, err := e.getUpdateAccountPermissionContract(vmInput) // Arguments[1] \u2014 attacker-chosen new permissions\n    ...\n    acc, err := e.accountsCacher.LoadUser(address)      // loads V\n    ...\n    // BUG: authorizes against vmInput.RecipientAddr (attacker-controlled), NOT vmInput.CallerAddr\n    if !e.contractHasValidPermission(acc.GetPermissions(), vmInput.RecipientAddr) {   // L91\n        return nil, errors.New(\"invalid permission operation\")\n    }\n    // overwrites V\u0027s entire permission set with attacker-supplied signers\n    resultCode, err := e.kappController.GetAccountsKApp().UpdatePermission(address, contract)\n    ...\n}\n```\n\n**(b) The check just name-matches `recipientAddr` against V\u0027s own signers** \u2014 same file:\n```go\nfunc (e *kleverUpdateAccountPermission) contractHasValidPermission(permissions []*state.Permission, recipientAddr []byte) bool {\n    for _, permission := range permissions {\n        for _, signer := range permission.Signers {\n            if !bytes.Equal(signer.Address, recipientAddr) {   // recipientAddr, not the authenticated caller\n                continue\n            }\n            if signer.Weight \u003e= permission.Threshold \u0026\u0026\n                permission.CheckPermissionGrantedForContracts(transaction.TXContract_UpdateAccountPermissionContractType) {\n                return true\n            }\n        }\n    }\n    return false\n}\n```\n\n**(c) The dispatch makes `RecipientAddr` attacker-controlled** \u2014 `kvm/vmhost/vmhooks/baseOps.go:2464` `prepareIndirectContractCallInput` (invoked when a contract calls the built-in via `ExecuteOnDestContext`):\n```go\ncontractCallInput := \u0026vmcommon.ContractCallInput{\n    VMInput: vmcommon.VMInput{\n        CallerAddr: sender,        // the calling contract (authenticated) \u2014 NOT used by the handler\n        Arguments:  data,          // attacker-chosen: [V, attackerPermissions]\n        ...\n    },\n    RecipientAddr: destination,    // the contract\u0027s chosen `dest` argument \u2014 attacker sets this to V\n    Function:      string(function),\n}\n```\n\n**(d) Every account with configured permissions is its own signer** \u2014 `core/kapp/accounts/accounts.go:1848` `createDefaultOwnerPermission` (appended by `UpdatePermission` when no Owner permission is supplied):\n```go\nreturn \u0026state.Permission{\n    Type:      state.Permission_Owner,   // Owner grants ALL contract types incl. type 22\n    Threshold: 1,\n    Signers: []*state.Key{\n        { Address: ownerAcc.AddressBytes(), Weight: 1 },   // the account signs for itself\n    },\n}\n```\nSo `contractHasValidPermission(V.perms, RecipientAddr=V)` finds V\u0027s own address as a `Weight 1 \u003e= Threshold 1` Owner signer \u2192 returns `true`.\n\n**(e) Contrast \u2014 the sibling handler does it correctly** \u2014 `core/kapp/builtInFunctions/kleverChangeOwnerAddress.go:86`:\n```go\ncallerAddress := vmInput.CallerAddr                        // authenticated caller\n...\nif !bytes.Equal(callerAddress, acc.GetOwnerAddress()) {    // checks the CALLER, not RecipientAddr\n    return nil, ErrOperationNotPermitted\n}\n```\n\n**Putting it together \u2014 the attacker\u0027s contract call:**\n```\nExecuteOnDestContext(\n    gas, dest = V,                       // \u2192 RecipientAddr = V\n    value = 0,\n    function = \"KleverUpdateAccountPermission\",\n    args = [ V, attackerOwnerPermsWithOnlyAttackerKey ],   // Arguments[0]=V, Arguments[1]=new perms\n)\n```\n\u2192 `CallerAddr = attackerContract` (ignored), `RecipientAddr = V`, `contractHasValidPermission(V.perms, V) == true` \u2192 V\u0027s permissions overwritten with the attacker\u0027s key as sole Owner signer. The attacker never held a key of V and provided no signature from V.\n\n### POC\n\nput the following poc testcase under /core/kapp/builtInFunctions/ \n\nPOC Code: https://gist.github.com/mabdullah22/a41f90aa5ba86bbebf121f739bd5f5e9\n\nRun:\n```\ncd klever-go\nGOTOOLCHAIN=auto go test ./core/kapp/builtInFunctions/ -run TestPoC_PermTakeover -v\n```\nOutput:\n```\nTAKEOVER CONFIRMED: caller=\"attacker-contract\" (attacker SC) rewrote account V=\"victim-account-V\"; new sole owner signer=\"attacker-key-EVIL\"\n--- PASS: TestPoC_PermTakeover\n--- PASS: TestPoC_PermTakeover_NoStoredPermsIsSafe\n```\nThe harm asserted is the takeover itself: after the call, V\u0027s permission set is a single Owner permission whose sole signer is the attacker\u0027s key; V\u0027s original owner signer is gone.\n\n### Impact\n\nFull takeover of **any account that has configured permissions**  i.e. every multisig / advanced-permission account , by an attacker who deploys a cheap smart contract and supplies only public on-chain addresses (no keys, no signatures from the victim). After takeover the attacker controls all of the victim\u0027s operations \u2192 theft or permanent lock of all the account\u0027s assets. Reachable via a permissionlessly-deployed contract (the plain-tx path is safe, so it is Critical-via-contract, not fully no-contract). No fork flag gates it.\n\nSeverity **Critical**: Impact High (full account/asset compromise)\n\n### Recommendation\n\nAuthorize against the authenticated caller, mirroring `kleverChangeOwnerAddress`:\n```go\nif !e.contractHasValidPermission(acc.GetPermissions(), vmInput.CallerAddr) { ... }\n```\nReconcile the SC-call authority model: on the built-in path `CallerAddr` is the calling contract, so a contract should only be able to update permissions of accounts that legitimately list *it* as an authorized signer \u2014 never an arbitrary victim. Consider also requiring the target account (`Arguments[0]`) to equal the authorized caller\u0027s account, matching the native `tx.GetSender()` model.",
  "id": "GHSA-97cv-x867-6xhm",
  "modified": "2026-09-23T19:27:08Z",
  "published": "2026-09-23T19:27:08Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/klever-io/klever-go/security/advisories/GHSA-97cv-x867-6xhm"
    },
    {
      "type": "WEB",
      "url": "https://github.com/klever-io/klever-go/commit/c58740eb74d7ee8f07db1e18a7d6214b5559ba32"
    },
    {
      "type": "WEB",
      "url": "https://gist.github.com/mabdullah22/a41f90aa5ba86bbebf121f739bd5f5e9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/klever-io/klever-go"
    },
    {
      "type": "WEB",
      "url": "https://github.com/klever-io/klever-go/releases/tag/v1.7.20"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Klever-Go Account takeover: `kleverUpdateAccountPermission` authorizes on attacker-controlled `RecipientAddr` instead of the authenticated caller"
}