CVE-2026-49343 Overview
Klever-Go, the Go implementation of the Klever blockchain protocol, contains a resource exhaustion flaw in its account-data trie syncers. In versions prior to 1.7.18, the syncDataTrie() function in both userAccountsSyncer.go and kappAccountsSyncer.go leaks throttler slots on error paths. StartProcessing() reserves a slot from NumGoRoutinesThrottler, but the matching EndProcessing() call executes only on successful completion or a duplicate-root early return. Any error from trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() permanently consumes a slot for the lifetime of the throttler. The weakness is tracked as CWE-400: Uncontrolled Resource Consumption.
Critical Impact
Attackers who repeatedly trigger trie-node sync failures or timeouts during bootstrap can exhaust the bounded throttler, causing SyncAccounts() to time out and blocking bootstrap for fresh, restarting, or resyncing nodes and validators.
Affected Products
- Klever-Go blockchain node implementation, all versions prior to 1.7.18
- Klever validators running the affected node software
- Fresh, restarting, or resyncing nodes performing epoch bootstrap
Discovery Timeline
- 2026-08-07 - CVE-2026-49343 published to NVD
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-49343
Vulnerability Analysis
The vulnerability is a denial-of-service condition caused by leaked concurrency slots in the account-data trie synchronization path. Klever-Go uses a NumGoRoutinesThrottler to bound the number of concurrent trie sync goroutines. Each call to syncDataTrie() acquires a slot through StartProcessing() and is expected to release it through EndProcessing() once the operation completes.
The throttler release is guarded only by the success path and the duplicate-root early return branch. When intermediate operations fail, the function returns without releasing the slot. Because the throttler has a fixed capacity, repeated failures deplete available slots. Once exhausted, subsequent sync attempts stall indefinitely and eventually surface as a timeout inside SyncAccounts().
Downstream, syncUserAccountsState() and syncKappAccountsState() abort the entire epoch bootstrap on any sync error. This converts a bounded goroutine leak into a full availability failure for the affected node.
Root Cause
The root cause is missing cleanup of a bounded resource on error paths. EndProcessing() is not invoked when trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() return an error, including the network-dependent timeout path. Idiomatic use of defer on the release call would have prevented the leak.
Attack Vector
An attacker on the network can repeatedly induce trie-node sync failures or timeouts during a target node's bootstrap phase. Because the vulnerable path is reached only during bootstrap or resync, attackers target nodes that are starting, restarting, or catching up. Each induced failure consumes one throttler slot permanently, and after enough failures the node cannot complete bootstrap. Full technical details are available in the GitHub Security Advisory GHSA-fw38-pc54-jvx9.
Detection Methods for CVE-2026-49343
Indicators of Compromise
- Repeated SyncAccounts() timeout errors in node logs during epoch bootstrap.
- Bootstrap failures in syncUserAccountsState() or syncKappAccountsState() on fresh, restarting, or resyncing nodes.
- Growing count of in-flight throttler reservations in NumGoRoutinesThrottler metrics without matching completions.
- Elevated rates of trie-node request timeouts from upstream peers during bootstrap windows.
Detection Strategies
- Monitor Klever-Go node logs for error returns from trie.NewTrie(), trie.NewTrieSyncer(), and trieSyncer.StartSyncing() correlated with bootstrap phases.
- Track the delta between StartProcessing() and EndProcessing() invocations on the account-data trie throttler over time; a persistent gap indicates a leak.
- Alert on any node that fails to complete epoch bootstrap within the expected time window.
Monitoring Recommendations
- Instrument bootstrap duration and success rate per node and validator, and alert on regressions.
- Capture peer-level metrics for trie-node request success and timeout rates to identify targeted disruption.
- Correlate validator downtime with peer connectivity churn to flag adversarial patterns against bootstrapping nodes.
How to Mitigate CVE-2026-49343
Immediate Actions Required
- Upgrade all Klever-Go nodes and validators to version 1.7.18 or later, available from the Klever-Go v1.7.18 release.
- Restart any node currently stuck in a failed bootstrap state after applying the patched binary.
- Prioritize patching validators and public-facing nodes that undergo frequent restart or resync cycles.
Patch Information
The issue is fixed in Klever-Go 1.7.18. The fix ensures that EndProcessing() on NumGoRoutinesThrottler is invoked on all return paths from syncDataTrie() in userAccountsSyncer.go and kappAccountsSyncer.go, including error and timeout paths. Release notes and source are published at the Klever-Go v1.7.18 release page.
Workarounds
- No official workaround exists; upgrading to 1.7.18 is the only supported remediation.
- As a temporary operational measure, restrict inbound peering to trusted peers to reduce the probability of induced trie-node sync failures during bootstrap.
- Restart affected nodes to reset the throttler state after a suspected exhaustion event, understanding this is not a durable fix.
# Upgrade Klever-Go to the patched release
git clone https://github.com/klever-io/klever-go.git
cd klever-go
git checkout v1.7.18
make build
# Verify the running version reports 1.7.18 or later
./klever-go --version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
