How severe is CVE-2026-56744?

No CVSS score has been assigned to CVE-2026-56744 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-56744?

CVE-2026-56744 affects the following packages: @bsv/wallet-toolbox (npm), @bsv/wallet-toolbox-client (npm), @bsv/wallet-toolbox-mobile (npm). Ecosystems affected: npm.

How do I fix CVE-2026-56744?

Update @bsv/wallet-toolbox to 2.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-56744 is resolved across your whole dependency graph.

How do I detect CVE-2026-56744 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @bsv/wallet-toolbox, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-56744 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-56744 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-56744 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-56744?

CVE-2026-56744 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-56744?

CVE-2026-56744 is classified as CWE-1288 (CWE-1288). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-56744 published, and has it been updated?

CVE-2026-56744 was published on September 24, 2026 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-56744 — @bsv/wallet-toolbox

Fix: bsv-blockchain/ts-stack@3a11f61

CVE-2026-56744 is a CWE-1288 vulnerability in @bsv/wallet-toolbox. A fix is available for @bsv/wallet-toolbox — see the affected versions and patch details below.

`@bsv/wallet-toolbox` / `-client` / `-mobile` don't verify storage-supplied recipient output scripts against caller-requested outputs in createAction (can redirect payments when using remote storage)

Also known asGHSA-36f9-7rg5-cpf8

Published

Sep 24, 2026

Updated

Oct 20, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Oct 16, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-56744.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs21th percentile — riskier than 21% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

3 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

13other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@bsv/wallet-toolboxnpm

3Kdownloads / week

@bsv/wallet-toolbox-clientnpm

3Kdownloads / week

@bsv/wallet-toolbox-mobilenpm

654downloads / week

Description

Reported by @echennells (Eric Chennells). Migrated from public issue #191 to a private advisory.

Affected: @bsv/wallet-toolbox / -client / -mobile. Verified in 2.1.21 and 2.1.21-parity-fix.2; the relevant code is the same at current HEAD

Summary: When createAction runs against a remote StorageClient, the storage server returns the outputs to build. buildSignableTransaction takes each non-change output's lockingScript from the storage response and signs it, without comparing it to the lockingScript the caller supplied in args.outputs. WalletPermissionsManager.createAction parses the built transaction and has args.outputs available, but uses the tx only for inputs and getFee(); it does not inspect tx.outputs. A storage provider that returns a different recipient script than requested will therefore have that script signed and broadcast, while the calling app and UI still show the originally requested recipient.

Relevant code:

signer/methods/buildSignableTransaction.js — non-change output lockingScript = asBsvSdkScript(out.lockingScript), sourced from the storage response; args.outputs is not consulted.
WalletPermissionsManager.js createAction — parses the built tx, derives spend from args.outputs satoshis + tx.getFee(), reads tx.inputs; does not read tx.outputs.
signer/methods/signAction.js, completeSignedTransaction.js — sign the as-built tx; no output comparison.

Context: Remote storage is a supported, default configuration (StorageClient over BRC-103 AuthFetch, default endpoint storage.babbage.systems, optional payment middleware). The mutual auth establishes the storage server's identity and protects the channel, but the contents it returns are not validated against the request. The attacker is the storage operator, or anyone who compromises it — not a passive network MITM. (StorageServer.processAction does compare the signed rawTx outputs to what storage stored, so a response-only MITM is rejected; an operator stores the substituted script from the start.)

Proof of concept: We ran a storage server that returns a substituted recipient output, and pointed a current yours-wallet build at it as its active storage provider. With the wallet otherwise unmodified, a payment requested to one address was built, signed, and broadcast paying a different address, the substitution was not surfaced anywhere in the wallet.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@bsv/wallet-toolbox`	≥ 1.1.47&&< 2.4.0	2.4.0`npm install @bsv/wallet-toolbox@2.4.0`
📦npm	`@bsv/wallet-toolbox-client`	≥ 1.1.47&&< 2.4.0	2.4.0`npm install @bsv/wallet-toolbox-client@2.4.0`
📦npm	`@bsv/wallet-toolbox-mobile`	≥ 1.3.21&&< 2.4.0	2.4.0`npm install @bsv/wallet-toolbox-mobile@2.4.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @bsv/wallet-toolbox, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @bsv/wallet-toolbox to 2.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-56744 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Reported by @echennells (Eric Chennells). Migrated from public issue #191 to a private advisory. **Affected:** `@bsv/wallet-toolbox` / `-client` / `-mobile`. Verified in `2.1.21` and `2.1.21-parity-fix.2`; the relevant code is the same at current HEAD **Summary:** When `createAction` runs against a remote `StorageClient`, the storage server returns the outputs to build. `buildSignableTransaction` takes each non-change output's `lockingScript` from the storage response and signs it, without comparing it to the `lockingScript` the caller supplied in `args.outputs`. `WalletPermissionsManager.cr

O3 Security · Impact-Aware SCA

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