CVE-2026-56744 bsv-blockchain CVE debrief

Who should care

Defenders responsible for `@bsv/wallet-toolbox`, `@bsv/wallet-toolbox-client`, and `@bsv/wallet-toolbox-mobile` deployments should assess exposure and prioritize remediation due to potential funds redirection and loss. Defenders should review compensating controls for exposed systems while remediation is scheduled and verified. Defenders should also track exceptions, retest remediated assets, and close the item only after evidence is documented.

Why it matters

Defenders should prioritize remediation due to potential funds redirection and loss, and implement compensating controls to prevent exploitation.

• Funds redirection due to malicious storage provider
• Potential loss of funds due to unverified transaction outputs
• Need for compensating controls such as local storage or independent verification
• Verification of transaction outputs required to prevent exploitation

Technical summary

The vulnerability is caused by a lack of verification of output locking scripts returned by the storage provider, allowing a malicious provider to substitute a recipient script or inject an additional output. This vulnerability affects `@bsv/wallet-toolbox`, `@bsv/wallet-toolbox-client`, and `@bsv/wallet-toolbox-mobile` packages. The vulnerability can be mitigated by upgrading to version 2.4.0 or later, or implementing compensating controls such as local storage or independent verification of transaction outputs. Defenders should prioritize upgrading to version 2.4.0 or later, or implementing compensating controls such as local storage or independent verification of transaction outputs.

Defensive priority

Defenders should prioritize upgrading to version 2.4.0 or later, or implementing compensating controls such as local storage or independent verification of transaction outputs.

Recommended defensive actions

• Upgrade to version 2.4.0 or later
• Implement compensating controls such as local storage
• Independently verify every transaction output's locking script and value against the original request before signing
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The vulnerability is caused by a lack of verification of output locking scripts returned by the storage provider, allowing a malicious provider to substitute a recipient script or inject an additional output. Source and npm publication history indicate that stable versions `@bsv/wallet-toolbox` and `@bsv/wallet-toolbox-client` from 1.1.47 through 2.3.3, and `@bsv/wallet-toolbox-mobile` from its initial 1.3.21 release through 2.3.3, are affected. Applications unable to upgrade should avoid remote `StorageClient` providers, use local or

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.