# CVE-2025-69287: BSV Blockchain SDK has an Authentication Signature Data Preparation Vulnerability

> Incorrect signature data preparation in the BSV Blockchain SDK allows attackers to bypass mutual authentication checks between peers.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 18 Feb 2026
- **Updated:** 18 Feb 2026
- **Also known as:** GHSA-vjpq-xx5g-qvmm

## What is CVE-2025-69287?

CVE-2025-69287 is a medium-severity authentication bypass vulnerability in bsv-blockchain ts-sdk, published on 18 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

The BSV Blockchain SDK is a unified TypeScript SDK for developing scalable apps on the BSV Blockchain. Prior to version 2.0.0, a cryptographic vulnerability in the TypeScript SDK's BRC-104 authentication implementation caused incorrect signature data preparation, resulting in signature incompatibility between SDK implementations and potential authentication bypass scenarios. The vulnerability was located in the `Peer.ts` file of the TypeScript SDK, specifically in the `processInitialRequest` and `processInitialResponse` methods where signature data is prepared for BRC-104 mutual authentication. The TypeScript SDK incorrectly prepared signature data by concatenating base64-encoded nonce strings (`message.initialNonce + sessionNonce`) then decoding the concatenated base64 string (`base64ToBytes(concatenatedString)`). This produced ~32-34 bytes of signature data instead of the correct 64 bytes. BRC-104 authentication relies on cryptographic signatures to establish mutual trust between peers. When signature data preparation is incorrect, signatures generated by the TypeScript SDK don't match those expected by Go/Python SDKs; cross-implementation authentication fails; and an attacker could potentially exploit this to bypass authentication checks. The fix in version 2.0.0 ensures all SDKs now produce identical cryptographic signatures, restoring proper mutual authentication across implementations.

Weakness: CWE-573 (Improper Following of Specification by Caller)

## Which versions are affected by CVE-2025-69287?

2 open source packages ship an affected version, including @bsv/sdk.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@bsv/sdk` | npm | All versions | 2.0.0 |
| `@bsv/sdk` | npm | All versions | 2.0.0 |

## How do I fix CVE-2025-69287?

Upgrade @bsv/sdk to 2.0.0 or later.

## Is CVE-2025-69287 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-69287 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-69287 and fix it if it is affected.

What it is: CVE-2025-69287 is a medium-severity authentication bypass vulnerability in bsv-blockchain ts-sdk, published on 18 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-69287 exists.

Affected packages and fixed versions:
- @bsv/sdk (npm): affected all versions; fixed in 2.0.0
- @bsv/sdk (npm): affected all versions; fixed in 2.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-69287/ (Markdown: https://insights.sbomify.com/CVE-2025-69287/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-69287
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-69287
- OSV: https://osv.dev/vulnerability/CVE-2025-69287

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-69287/
Summaries are generated and may contain mistakes; the official description above is the record.