CVE-2026-46403: Klever-Go Privilege Escalation Vulnerability

CVE-2026-46403 Overview

CVE-2026-46403 affects Klever-Go, the Go implementation of the Klever blockchain protocol. The Klever Virtual Machine (KVM) exposes ExecuteReadOnlyWithTypedArguments as a read-only execution mechanism. However, the indirect contract delete and upgrade paths fail to reject execution when runtime.ReadOnly() returns true. A contract reached through read-only execution can invoke the production delete hook against a target contract it owns. The delete path appends the target address to vmOutput.DeletedAccounts, which the smart contract processor later applies to chain state. This breaks the isolation boundary that read-only calls are supposed to guarantee. The issue is fixed in version 1.7.17.

Critical Impact
A callee reached through a read-only KVM invocation can trigger contract deletion and upgrade operations, allowing state-changing side effects from calls that should be side-effect free.

Affected Products

Klever-Go versions prior to 1.7.17
Klever Virtual Machine (KVM) read-only execution subsystem
Klever blockchain smart contract processor

Discovery Timeline

2026-07-21 - CVE-2026-46403 published to NVD
2026-07-23 - Last updated in NVD database

Technical Details for CVE-2026-46403

Vulnerability Analysis

The vulnerability is a protection mechanism failure [CWE-693] in the KVM host-core execution path. The ExecuteReadOnlyWithTypedArguments hook saves the previous read-only state, sets runtime.SetReadOnly(true), executes the destination context, and then restores the previous state. This mechanism relies on individual host-core hooks to check runtime.ReadOnly() before performing state-changing operations. The delete and upgrade paths never consulted that flag, so any contract executed under a read-only frame could still emit DeletedAccounts entries and upgrade instructions. The output context then merges these fields into the caller output, and the smart contract processor applies them to chain state after VM execution completes.

Root Cause

Read-only mode is applied as runtime state but is not enforced by the state-changing delete and upgrade host-core paths. The invariant that a read-only frame must produce a side-effect-free vmOutput was assumed rather than checked at each mutation site. Contract owners retained authority to call the production delete hook even when the current execution frame was flagged read-only.

Attack Vector

An attacker deploys or controls a contract that is invoked through ExecuteReadOnlyWithTypedArguments from a caller expecting a pure inspection. During that invocation, the attacker-controlled callee calls the delete hook against a contract it owns. The delete instruction is captured in vmOutput.DeletedAccounts and propagates up to the caller output. When the smart contract processor commits the VM output, the target account is removed from chain state. The same class of bypass applies to upgrade operations and other VM output fields that later mutate state.

// Patch context from fixed release (v1.7.17)
// New sentinel errors introduced alongside the read-only enforcement fix
var ErrTooManyItemsInBatch = errors.New("too many items in batch")
var ErrDecompressionTooLarge = errors.New("decompressed payload exceeds maximum allowed size")
var ErrDecompressedSizeMismatch = errors.New("decompressed payload size does not match advertised data size")

// Fixed behavior (described): delete and upgrade host-core paths now check
// runtime.ReadOnly() and abort execution before appending to
// vmOutput.DeletedAccounts or emitting upgrade instructions.

Source: Klever-Go Fix Commit

Detection Methods for CVE-2026-46403

Indicators of Compromise

Unexpected entries in vmOutput.DeletedAccounts originating from transactions whose top-level call is a read-only inspection
Contract accounts removed from chain state without a corresponding direct delete transaction from the owner
Upgrade code changes to a contract that were emitted by a callee invoked through ExecuteReadOnlyWithTypedArguments

Detection Strategies

Audit historical VM output logs for DeletedAccounts and upgrade fields produced by execution frames that entered through the read-only hook
Correlate deleted contract addresses with the calling contract's ownership graph to detect deletes triggered through indirect read-only paths
Add regression tests covering delete, upgrade, storage writes, and value transfers under a read-only frame, as introduced in v1.7.17

Monitoring Recommendations

Alert on node versions below 1.7.17 running in validator or archive roles
Monitor for anomalous rates of contract deletion or upgrade operations relative to historical baselines
Track invocations of ExecuteReadOnlyWithTypedArguments where the resulting vmOutput contains any non-empty state-mutation field

How to Mitigate CVE-2026-46403

Immediate Actions Required

Upgrade all Klever-Go nodes to version 1.7.17 or later
Review contracts that expose owner-authorized delete or upgrade entry points and confirm callers cannot be reached through read-only execution
Replay recent VM outputs against the fixed release to identify state changes that would have been rejected under the enforced invariant

Patch Information

The fix is available in Klever-Go v1.7.17. Contract delete and upgrade host-core paths now reject execution when runtime.ReadOnly() is true. The invariant is regression-tested for delete, upgrade, storage writes, value transfers, and any VM output field that can later mutate chain state. See the Klever-Go Security Advisory GHSA-jc6w-wmfc-fh33 and the remediation commit.

Workarounds

No supported workaround exists short of upgrading to v1.7.17
As a temporary measure, restrict read-only entry points on deployed contracts to disallow calls into contracts that expose owner-controlled delete or upgrade functions
Disable or gate ExecuteReadOnlyWithTypedArguments usage in application logic until nodes are patched

bash

# Upgrade Klever-Go node to the fixed release
git fetch --tags
git checkout v1.7.17
go build -o klever-node ./cmd/node
systemctl restart klever-node