CVE-2026-82405: Klever-Go Account takeover: `kleverUpdateAccountPermission` authorizes on attacker-controlled `RecipientAddr` instead of the authenticated caller

The VM built-in function KleverUpdateAccountPermission (registered always-active, creator.go:381-390 / core/vmconstants.go:234) rewrites an account’s 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().

Mechanism:

1. 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 >= Threshold in the target account’s permissions and the permission grants UpdateAccountPermissionContractType.
2. 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.
3. 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’s signer addresses meeting threshold all public on-chain.) Accounts with no stored permissions have empty GetPermissions() and are immune.
4. Overwrite is unrestricted: UpdatePermission(V, attackerContract) (accounts.go:1863) replaces V’s permission set with attacker-supplied signers; if the attacker supplies an Owner-type permission, no default is appended and V’s prior control is fully evicted.