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bsv-sdk ARC broadcaster treats INVALID/MALFORMED/ORPHAN responses as successful broadcasts

High severity GitHub Reviewed Published Apr 8, 2026 in sgbett/bsv-ruby-sdk • Updated Apr 9, 2026

Package

bundler bsv-sdk (RubyGems)

Affected versions

>= 0.1.0, < 0.8.2

Patched versions

0.8.2

Description

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

References

@sgbett sgbett published to sgbett/bsv-ruby-sdk Apr 8, 2026
Published by the National Vulnerability Database Apr 9, 2026
Published to the GitHub Advisory Database Apr 9, 2026
Reviewed Apr 9, 2026
Last updated Apr 9, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(9th percentile)

Weaknesses

Improper Check for Unusual or Exceptional Conditions

The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. Learn more on MITRE.

CVE ID

CVE-2026-40069

GHSA ID

GHSA-9hfr-gw99-8rhx

Source code

Credits

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