# CVE-2026-55764: klever-go SFT add-quantity int64 overflow bypasses MaxSupply

Source: https://junglewise.ai/threats/cve-2026-55764-klever-go-sft-add-quantity-int64-overflow-bypasses-maxsupply  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-28. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-55764 · Severity: high · CVSS 4 · Published 2026-08-28

The Klever blockchain library's semi-fungible token (SFT) minting function fails to validate integer overflow when adding tokens to circulation. A mint-role holder can mint approximately 9.2 quintillion tokens in a single transaction, bypassing a declared supply cap and corrupting the on-chain circulation counter. This allows unauthorized token creation at massive scale with no corresponding debit.

Technologies: [github.com/klever-io/klever-go (Go)](https://junglewise.ai/threats/technologies/github-com-klever-io-klever-go), [Klever.io Klever-Go](https://junglewise.ai/threats/technologies/klever-go). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Klever.io](https://junglewise.ai/threats/vendors/klever-io).

## Quick answers

**Is CVE-2026-55764 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55764 being exploited in the wild.

**How severe is CVE-2026-55764?** High severity, with a CVSS score of 4, published 28 August 2026.

**Which products and versions are affected?** github.com/klever-io/klever-go (Go) < 1.7.19, SEMVER:introduced=0,fixed=1.7.19; Klever.io Klever-Go < 1.7.19.

**Is there a fix for CVE-2026-55764?** Yes. github.com/klever-io/klever-go (Go): upgrade to 1.7.19 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55764 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-55764?** Check whether you run github.com/klever-io/klever-go (Go) or Klever.io Klever-Go at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/klever-io/klever-go (Go): upgrade to 1.7.19 or later

  ```sh
  go get github.com/klever-io/klever-go@v1.7.19
  ```


## Technical details

The vulnerability is an integer overflow in the SFTAddCirculation function (core/kapp/systemAccount/systemAcount.go:132-138). The code performs an unguarded addition `meta.Circulation += amount` where amount is a raw int64 parameter from the contract with no upstream bounds. When amount is large enough (e.g., MaxInt64), the addition overflows and wraps to a negative value. The subsequent cap check `if meta.Circulation > meta.MaxSupply && meta.MaxSupply != 0` evaluates to false because a negative number is not greater than MaxSupply, allowing the function to return nil and persist the corrupted circulation value. The fungible mint path is protected by a post-increment `MintedValue <= 0` guard that this code path lacks. Attack vector is network-based; requires mint-role holder authorization (asset owner or delegated role). A proof-of-concept unit test confirms the overflow and bypass, and live on-chain testing demonstrates minting MaxInt64 tokens past a declared cap of 1000 with result code Ok.

## Affected products

- klever-io klever-go < 1.7.19

## Identifiers

- CVE-2026-55764
- GHSA-mrpp-v6pg-p54x
- GO-2026-6330

## Timeline

- 2026-06-22: disclosed
- 2026-06-22: patched: Fixed in version 1.7.19
- 2026-08-28: other: CVE-2026-55764 published

## References

- [https://api.github.com/users/nickgs1337](https://api.github.com/users/nickgs1337)
- [https://github.com/nickgs1337](https://github.com/nickgs1337)
- [https://api.github.com/users/nickgs1337/gists%7B/gist_id%7D](https://api.github.com/users/nickgs1337/gists%7B/gist_id%7D)
- [https://api.github.com/users/nickgs1337/repos](https://api.github.com/users/nickgs1337/repos)
- [https://avatars.githubusercontent.com/u/16809614?v=4](https://avatars.githubusercontent.com/u/16809614?v=4)
- [https://api.github.com/users/nickgs1337/events%7B/privacy%7D](https://api.github.com/users/nickgs1337/events%7B/privacy%7D)

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