How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

352,262

Total vulnerabilities in the database

CVE-2026-49343 — github.com/klever-io/klever-go

Uncontrolled Resource Consumption

Summary

The account-data trie syncers leak bounded throttler slots on error paths in syncDataTrie(). Each failed trie sync permanently consumes one slot from the NumGoRoutinesThrottler, and the slot is never returned unless the sync succeeds or the root hash was already present.

I confirmed this on the current default branch develop at commit 9640d63 (observed on May 20, 2026). I also confirmed the bug with a runtime PoC using the real timeout path in trieSyncer.StartSyncing(): two timed-out sync attempts are enough to exhaust a throttler with capacity 2.

This affects the epoch bootstrap path because syncUserAccountsState() and syncKappAccountsState() create bounded throttlers and abort bootstrap immediately if the syncer returns an error. Once enough trie-root sync attempts fail, the syncer cannot make forward progress and bootstrap fails.

Affected Components

data/syncer/userAccountsSyncer.go
data/syncer/kappAccountsSyncer.go
data/trie/sync.go
core/throttler/numGoRoutinesThrottler.go
core/bootstrap/process.go

Affected Version

Verified on:

develop HEAD 9640d63

Please check whether the same code is present in supported 1.7.x releases.

Suggested Severity

High

Vulnerability Details

Root Cause

Both account-data syncers call StartProcessing() before creating / starting the trie syncer, but they only call EndProcessing() on the success path and on the duplicate-root early return.

userAccountsSyncer.syncDataTrie():

func (u *userAccountsSyncer) syncDataTrie(rootHash []byte, ssh data.SyncStatisticsHandler, ctx context.Context) error {
    u.throttler.StartProcessing()

    u.syncerMutex.Lock()
    if _, ok := u.dataTries[string(rootHash)]; ok {
        u.syncerMutex.Unlock()
        u.throttler.EndProcessing()
        return nil
    }

    dataTrie, err := trie.NewTrie(...)
    if err != nil {
        u.syncerMutex.Unlock()
        return err
    }

    trieSyncer, err := trie.NewTrieSyncer(arg)
    if err != nil {
        u.syncerMutex.Unlock()
        return err
    }

    u.syncerMutex.Unlock()

    err = trieSyncer.StartSyncing(rootHash, ctx)
    if err != nil {
        return err
    }

    u.throttler.EndProcessing()
    return nil
}

The same bug exists in kappAccountsSyncer.syncDataTrie().

Missing slot release paths

After StartProcessing(), the following error paths return without EndProcessing():

trie.NewTrie(...) returns an error
trie.NewTrieSyncer(...) returns an error
trieSyncer.StartSyncing(...) returns an error

Why this matters

NumGoRoutinesThrottler is a strict bounded counter:

  func (ngrt *NumGoRoutinesThrottler) CanProcess() bool {
      valCounter := atomic.LoadInt32(&amp;ngrt.counter)
      return valCounter &lt; ngrt.max
  }

  func (ngrt *NumGoRoutinesThrottler) StartProcessing() {
      atomic.AddInt32(&amp;ngrt.counter, 1)
  }

  func (ngrt *NumGoRoutinesThrottler) EndProcessing() {
      atomic.AddInt32(&amp;ngrt.counter, -1)
  }

  Once leaked, a slot remains consumed for the lifetime of that throttler instance.

  The parent loops in both syncers wait for capacity before starting the next account-data trie sync:

  for !u.throttler.CanProcess() {
      select {
      case &lt;-time.After(timeBetweenRetries):
          continue
      case &lt;-ctx.Done():
          return common.ErrTimeIsOut
      }
  }

So after enough failures, further roots stop progressing and the sync operation eventually returns time is out.

Bootstrap impact

Epoch bootstrap uses these syncers directly and aborts on any error:

  err = e.syncUserAccountsState(e.epochStartMeta.Header.TrieRoot)
  if err != nil {
      return nil, nil, err
  }

  err = e.syncKappAccountsState(e.epochStartMeta.Header.KAppsTrieRoot)
  if err != nil {
      return nil, nil, err
  }

The throttlers for these paths are real bounded throttlers created from numConcurrentTrieSyncers.

Proof of Concept

I verified the bug with the real timeout path, not only with a canceled context.

The PoC below uses:

a real NumGoRoutinesThrottler with capacity 2
a real trieSyncer.StartSyncing()
an empty trie-node cache and a request handler that never supplies nodes
a short sync timeout (1s) so StartSyncing() returns trie.ErrTimeIsOut

After the first failed sync, one slot remains leaked. After the second failed sync, the throttler is exhausted.

PoC test

  package syncer

  import (
        &quot;context&quot;
        &quot;testing&quot;
        &quot;time&quot;

        commonmock &quot;github.com/klever-io/klever-go/common/mock&quot;
        corethrottler &quot;github.com/klever-io/klever-go/core/throttler&quot;
        &quot;github.com/klever-io/klever-go/data&quot;
        &quot;github.com/klever-io/klever-go/data/trie&quot;
        triestats &quot;github.com/klever-io/klever-go/data/trie/statistics&quot;
        &quot;github.com/stretchr/testify/require&quot;
  )

  func newBaseSyncerForTimeoutPOC(t *testing.T) *baseAccountsSyncer {
        t.Helper()

        storageManager, err := trie.NewTrieStorageManagerWithoutPruning(commonmock.NewMemDbMock())
        require.NoError(t, err)

        return &amp;baseAccountsSyncer{
                hasher:                    commonmock.HasherMock{},
                marshalizer:               &amp;commonmock.MarshalizerMock{},
                trieSyncers:               make(map[string]data.TrieSyncer),
                dataTries:                 make(map[string]data.Trie),
                trieStorageManager:        storageManager,
                requestHandler:            &amp;commonmock.RequestHandlerStub{},
                timeout:                   time.Second,
                cacher:                    commonmock.NewCacherStub(),
                maxTrieLevelInMemory:      5,
                name:                      &quot;timeout-poc&quot;,
                maxHardCapForMissingNodes: 1,
        }
  }

  func TestPOC_UserAccountsSyncer_LeaksThrottlerSlotOnTrieTimeout(t *testing.T) {
        thr, err := corethrottler.NewNumGoRoutinesThrottler(2)
        require.NoError(t, err)

        s := &amp;userAccountsSyncer{
                baseAccountsSyncer: newBaseSyncerForTimeoutPOC(t),
                throttler:          thr,
        }

        err = s.syncDataTrie([]byte(&quot;missing-root-1&quot;), triestats.NewTrieSyncStatistics(), context.Background())
        require.ErrorIs(t, err, trie.ErrTimeIsOut)
        require.True(t, thr.CanProcess())

        err = s.syncDataTrie([]byte(&quot;missing-root-2&quot;), triestats.NewTrieSyncStatistics(), context.Background())
        require.ErrorIs(t, err, trie.ErrTimeIsOut)
        require.False(t, thr.CanProcess())
  }

  func TestPOC_KappAccountsSyncer_LeaksThrottlerSlotOnTrieTimeout(t *testing.T) {
        thr, err := corethrottler.NewNumGoRoutinesThrottler(2)
        require.NoError(t, err)

        s := &amp;kappAccountsSyncer{
                baseAccountsSyncer: newBaseSyncerForTimeoutPOC(t),
                throttler:          thr,
        }

        err = s.syncDataTrie([]byte(&quot;missing-root-1&quot;), triestats.NewTrieSyncStatistics(), context.Background())
        require.ErrorIs(t, err, trie.ErrTimeIsOut)
        require.True(t, thr.CanProcess())

        err = s.syncDataTrie([]byte(&quot;missing-root-2&quot;), triestats.NewTrieSyncStatistics(), context.Background())
        require.ErrorIs(t, err, trie.ErrTimeIsOut)
        require.False(t, thr.CanProcess())
  }

Command used

  go test ./data/syncer -run &#039;TestPOC_(User|Kapp)AccountsSyncer_LeaksThrottlerSlotOnTrieTimeout&#039; -count=1

Result

  ok    github.com/klever-io/klever-go/data/syncer      4.005s

This confirms the leak with the real timeout path from trieSyncer.StartSyncing().

Impact

An attacker who can repeatedly cause trie-node sync failures or timeouts during bootstrap can consume the bounded sync throttler until no capacity remains.

Once enough slots are leaked:

additional account-data trie sync attempts stop making progress
the parent loop waits until context timeout
SyncAccounts() fails
epoch bootstrap fails

This is a core node availability issue. It affects fresh/restarting nodes and validators that need to bootstrap or resync state.

This is not a theoretical issue:

StartSyncing() performs network-dependent trie-node retrieval
it already has explicit timeout / failure paths
the leaked throttler slots are confirmed by runtime PoC

Recommended Fix

Release the slot with defer immediately after StartProcessing() and cancel the defer only if ownership is intentionally transferred, which is not the case here.

Example fix pattern:

  func (u *userAccountsSyncer) syncDataTrie(rootHash []byte, ssh data.SyncStatisticsHandler, ctx context.Context) error {
      u.throttler.StartProcessing()
      defer u.throttler.EndProcessing()

      u.syncerMutex.Lock()
      defer u.syncerMutex.Unlock()

      if _, ok := u.dataTries[string(rootHash)]; ok {
          return nil
      }

      dataTrie, err := trie.NewTrie(...)
      if err != nil {
          return err
      }

      trieSyncer, err := trie.NewTrieSyncer(arg)
      if err != nil {
          return err
      }

      u.trieSyncers[string(rootHash)] = trieSyncer
      return trieSyncer.StartSyncing(rootHash, ctx)
  }

The same pattern should be applied to:

data/syncer/userAccountsSyncer.go
data/syncer/kappAccountsSyncer.go

References

data/syncer/userAccountsSyncer.go
data/syncer/kappAccountsSyncer.go
data/trie/sync.go
core/throttler/numGoRoutinesThrottler.go
core/bootstrap/process.go
SECURITY.md

Published: Jun 5, 2026
Updated: Jun 5, 2026
CVE: CVE-2026-49343
GHSA: GHSA-fw38-pc54-jvx9
Severity: Medium
Exploit:
CISA KEV:

CVSS v3:

Severity: Medium
Score: 5.9
AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

Affected Software
References

Software	From	Fixed in
github.com/klever-io/klever-go	-	1.7.18

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.