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CVE-2026-49343

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS

5.9 MediumFix available

Klever-Go is the Go implementation of the Klever blockchain protocol. In versions prior to 1.7.18, the account-data trie syncers are vulnerable to a resource-exhaustion flaw that leaks bounded throttler slots on error paths. In syncDataTrie() (in both userAccountsSyncer.go and kappAccountsSyncer.go), StartProcessing() reserves a slot from the NumGoRoutinesThrottler, but the corresponding EndProcessing() is only called on the success path and on the duplicate-root early return. As a result, any error from trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() (including the network-dependent timeout path) permanently consumes one slot for the lifetime of the throttler. An attacker who can repeatedly cause trie-node sync failures or timeouts during bootstrap can exhaust the bounded throttler, after which further account-data trie syncs stop making progress and SyncAccounts() returns a timeout. Because epoch bootstrap in syncUserAccountsState() and syncKappAccountsState() aborts on any such error, this causes bootstrap to fail, a core availability issue affecting fresh, restarting, or resyncing nodes and validators. This issue is fixed in version 1.7.18.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.41%Up 0.4 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.9

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS

Klever-Go is the Go implementation of the Klever blockchain protocol. In versions prior to 1.7.18, the account-data trie syncers are vulnerable to a resource-exhaustion flaw that leaks bounded throttler slots on error paths. In syncDataTrie() (in both userAccountsSyncer.go and kappAccountsSyncer.go), StartProcessing() reserves a slot from the NumGoRoutinesThrottler, but the corresponding EndProcessing() is only called on the success path and on the duplicate-root early return. As a result, any error from trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() (including the network-dependent timeout path) permanently consumes one slot for the lifetime of the throttler. An attacker who can repeatedly cause trie-node sync failures or timeouts during bootstrap can exhaust the bounded throttler, after which further account-data trie syncs stop making progress and SyncAccounts() returns a timeout. Because epoch bootstrap in syncUserAccountsState() and syncKappAccountsState() aborts on any such error, this causes bootstrap to fail, a core availability issue affecting fresh, restarting, or resyncing nodes and validators. This issue is fixed in version 1.7.18.

Record
CVE-2026-49343
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
EUVDEUVD-2026-54716 5.9

Klever-Go is the Go implementation of the Klever blockchain protocol. In versions prior to 1.7.18, the account-data trie syncers are vulnerable to a resource-exhaustion flaw that leaks bounded throttler slots on error paths. In syncDataTrie() (in both userAccountsSyncer.go and kappAccountsSyncer.go), StartProcessing() reserves a slot from the NumGoRoutinesThrottler, but the corresponding EndProcessing() is only called on the success path and on the duplicate-root early return. As a result, any error from trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() (including the network-dependent timeout path) permanently consumes one slot for the lifetime of the throttler. An attacker who can repeatedly cause trie-node sync failures or timeouts during bootstrap can exhaust the bounded throttler, after which further account-data trie syncs stop making progress and SyncAccounts() returns a timeout. Because epoch bootstrap in syncUserAccountsState() and syncKappAccountsState() aborts on any such error, this causes bootstrap to fail, a core availability issue affecting fresh, restarting, or resyncing nodes and validators. This issue is fixed in version 1.7.18.

Record
EUVD-2026-54716
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-fw38-pc54-jvx9 5.9

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS

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():

  1. trie.NewTrie(...) returns an error
  2. trie.NewTrieSyncer(...) returns an error
  3. trieSyncer.StartSyncing(...) returns an error

Why this matters

NumGoRoutinesThrottler is a strict bounded counter:

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

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

  func (ngrt *NumGoRoutinesThrottler) EndProcessing() {
      atomic.AddInt32(&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 <-time.After(timeBetweenRetries):
          continue
      case <-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…

Record
GHSA-fw38-pc54-jvx9
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
NVD 5.9

Klever-Go is the Go implementation of the Klever blockchain protocol. In versions prior to 1.7.18, the account-data trie syncers are vulnerable to a resource-exhaustion flaw that leaks bounded throttler slots on error paths. In syncDataTrie() (in both userAccountsSyncer.go and kappAccountsSyncer.go), StartProcessing() reserves a slot from the NumGoRoutinesThrottler, but the corresponding EndProcessing() is only called on the success path and on the duplicate-root early return. As a result, any error from trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() (including the network-dependent timeout path) permanently consumes one slot for the lifetime of the throttler. An attacker who can repeatedly cause trie-node sync failures or timeouts during bootstrap can exhaust the bounded throttler, after which further account-data trie syncs stop making progress and SyncAccounts() returns a timeout. Because epoch bootstrap in syncUserAccountsState() and syncKappAccountsState() aborts on any such error, this causes bootstrap to fail, a core availability issue affecting fresh, restarting, or resyncing nodes and validators. This issue is fixed in version 1.7.18.

Record
CVE-2026-49343
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
OSV 5.9

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS

Klever-Go is the Go implementation of the Klever blockchain protocol. In versions prior to 1.7.18, the account-data trie syncers are vulnerable to a resource-exhaustion flaw that leaks bounded throttler slots on error paths. In syncDataTrie() (in both userAccountsSyncer.go and kappAccountsSyncer.go), StartProcessing() reserves a slot from the NumGoRoutinesThrottler, but the corresponding EndProcessing() is only called on the success path and on the duplicate-root early return. As a result, any error from trie.NewTrie(), trie.NewTrieSyncer(), or trieSyncer.StartSyncing() (including the network-dependent timeout path) permanently consumes one slot for the lifetime of the throttler. An attacker who can repeatedly cause trie-node sync failures or timeouts during bootstrap can exhaust the bounded throttler, after which further account-data trie syncs stop making progress and SyncAccounts() returns a timeout. Because epoch bootstrap in syncUserAccountsState() and syncKappAccountsState() aborts on any such error, this causes bootstrap to fail, a core availability issue affecting fresh, restarting, or resyncing nodes and validators. This issue is fixed in version 1.7.18.

Record
CVE-2026-49343
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
OSVGHSA-fw38-pc54-jvx9 5.9

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS

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():

  1. trie.NewTrie(...) returns an error
  2. trie.NewTrieSyncer(...) returns an error
  3. trieSyncer.StartSyncing(...) returns an error

Why this matters

NumGoRoutinesThrottler is a strict bounded counter:

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

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

  func (ngrt *NumGoRoutinesThrottler) EndProcessing() {
      atomic.AddInt32(&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 <-time.After(timeBetweenRetries):
          continue
      case <-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…

Record
GHSA-fw38-pc54-jvx9
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
OSVGO-2026-5379 No score

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS in github.com/klever-io/klever-go

Klever-Go KVM: Throttler slot leak in trie account-data sync causes epoch bootstrap / state sync DoS in github.com/klever-io/klever-go

Record
GO-2026-5379
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/klever-io/klever-go
Go
 before 1.7.18
1.7.18
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-49343 is a medium vulnerability (CVSS 5.9) in Klever-io Klever-go, published June 5, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in github.com/klever-io/klever-go 1.7.18.

References

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