GHSA-9hfr-gw99-8rhx

# ARC broadcaster treats failure statuses as successful broadcasts

## Summary

`BSV::Network::ARC`'s failure detection only recognises `REJECTED` and `DOUBLE_SPEND_ATTEMPTED`. ARC responses with `txStatus` values of `INVALID`, `MALFORMED`, `MINED_IN_STALE_BLOCK`, or any `ORPHAN`-containing `extraInfo` / `txStatus` are silently treated as successful broadcasts. Applications that gate actions on broadcaster success are tricked into trusting transactions that were never accepted by the network.

## Details

`lib/bsv/network/arc.rb` (lines ~74-100 in the affected code) uses a narrow failure predicate compared to the TypeScript reference SDK. The TS broadcaster additionally recognises:

- `INVALID` - `MALFORMED` - `MINED_IN_STALE_BLOCK` - Any response containing `ORPHAN` in `extraInfo` or `txStatus`

The Ruby implementation omits all of these, so ARC responses carrying any of these statuses are returned to the caller as successful broadcasts.

Additional divergences in the same module compound the risk:

- `Content-Type` is sent as `application/octet-stream`; the TS reference sends `application/json` with a `{ rawTx: <hex> }` body (EF form where source transactions are available). - The headers `XDeployment-ID`, `X-CallbackUrl`, and `X-CallbackToken` are not sent.

The immediate security-relevant defect is the missing failure statuses; the other divergences are fixed in the same patch for protocol compliance.

## Impact

Integrity: callers receive a success response for broadcasts that were actually rejected by the ARC endpoint. Applications and downstream gems that gate actions on broadcaster success — releasing goods, marking invoices paid, treating a token as minted, progressing a workflow — are tricked into trusting transactions that were never broadcast.

This is an integrity bug with security consequences. It does not disclose information (confidentiality unaffected) and does not affect availability.

## CVSS rationale

`AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N` → **7.5 (High)**

- **AV:N** — network-reachable. - **AC:L** — no specialised access conditions are required. Triggering any of the unhandled failure statuses is not meaningfully harder than broadcasting a transaction at all: a malformed or invalid transaction, an orphan condition from a transient fork, or a hostile/misbehaving ARC endpoint returning one of these statuses is sufficient. The attacker does not need to defeat any mitigation or race a specific window — the bug is that the code path doesn't exist at all. - **PR:N** — no privileges required. - **UI:N** — no user interaction. - **C:N** — no confidentiality impact. - **I:H** — downstream integrity decisions are taken on non-broadcast transactions. - **A:N** — no availability impact.

## Affected versions

The ARC broadcaster was introduced in commit `a1f2e62` ("feat(network): add ARC broadcaster with injectable HTTP client") on 2026-02-08 and first released in **v0.1.0**. The narrow failure predicate has been present since introduction. Every release up to and including **v0.8.1** is affected.

Affected range: `>= 0.1.0, < 0.8.2`.

## Patches

Upgrade to `bsv-sdk >= 0.8.2`. The fix:

- Expands the failure predicate (`REJECTED_STATUSES` + `ORPHAN` substring check on both `txStatus` and `extraInfo`) to include `INVALID`, `MALFORMED`, `MINED_IN_STALE_BLOCK`, and any orphan-containing response, matching the TypeScript reference. - Switches `Content-Type` to `application/json` with a `{ rawTx: <hex> }` body, preferring Extended Format (BRC-30) hex when every input has `source_satoshis` and `source_locking_script` populated and falling back to plain raw-tx hex otherwise. - Adds support for the `XDeployment-ID` (default: random `bsv-ruby-sdk-<hex>`), `X-CallbackUrl`, and `X-CallbackToken` headers via new constructor keyword arguments.

Fixed in sgbett/bsv-ruby-sdk#306.

### Note for `bsv-wallet` consumers

The sibling gem `bsv-wallet` (published from the same repository) is not independently vulnerable — `lib/bsv/network/arc.rb` is not bundled into the wallet gem's `files` list. However, `bsv-wallet` runtime-depends on `bsv-sdk`, so a consumer of `bsv-wallet` that also invokes the ARC broadcaster is transitively exposed whenever `Gemfile.lock` resolves to a vulnerable `bsv-sdk` version. `bsv-wallet >= 0.3.4` tightens its `bsv-sdk` constraint to `>= 0.8.2, < 1.0`, so upgrading either gem is sufficient to pull in the fix.

## Workarounds

If upgrading is not immediately possible:

- Verify broadcast results out-of-band (e.g. query a block explorer or WhatsOnChain) before treating a transaction as broadcast. - Do not gate integrity-critical actions solely on the ARC broadcaster's success response.

## Credit

Identified during the 2026-04-08 cross-SDK compliance review, tracked as finding F5.13.

## References

- HLR: sgbett/bsv-ruby-sdk#305 - Fix PR: sgbett/bsv-ruby-sdk#306 - Compliance review: [`.architecture/reviews/20260408-cross-sdk-compliance-review.md`](../../.architecture/reviews/20260408-cross-sdk-compliance-review.md) - TypeScript reference: `ARC` class in `@bsv/sdk`