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Malicious code in multichain-rpc (RubyGems)

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • RubyGems multichain-rpc

    Affected
    >= 0.9.1, <= 0.9.1
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
not scored
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

--- _-= Per source details. Do not edit below this line.=-_

Source: amazon-inspector (b5765482ebcff5ac393edb3ce06164e7c697a00aa7e32c92b1272dc20184b424) The gem's extconf.rb, executed automatically by `gem install` as a native-extension build step, base64-decodes a Ruby payload and runs it via `eval` inside a double-forked, stdio-detached background process. The payload opens a TCP socket to the hardcoded host 45.138.12.177 on port 8089 and bridges it to `/bin/sh`, giving the remote operator an interactive shell on the installer's machine. Execution is gated by developer-host heuristics (presence of ~/.ssh, ~/.gitconfig, ~/.npmrc, ~/.gem/credentials, ~/.bundle, uptime > 1800s) and explicit anti-analysis checks that skip CI, ephemeral, generated-user, and sandbox environments, with a 20-40 minute delay before firing. The rest of the gem is cover: lib/multichain_rpc.rb exports only stub methods (`build_id` returning 'ok', `healthy?` returning true), the README advertises an unrelated…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from osv record MAL-2026-17791

Agent brief

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# Patch Next advisory brief: mal-2026-17791

Advisory: Malicious code in multichain-rpc (RubyGems)
IDs: mal-2026-17791
Record: https://patchnext.com/advisories/mal-2026-17791 (revision 1, source checked 23 Oct 2026, 22:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems multichain-rpc: affected >= 0.9.1, <= 0.9.1

## Suggested inspection (read-only)
- RubyGems multichain-rpc: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on multichain-rpc.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/MAL-2026-17791 (OSV record MAL-2026-17791 lists affected ranges: RubyGems multichain-rpc >=0.9.1 <=0.9.1)

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