nft-metadata-resolver

Details

**Severity:** Critical

**Affected versions:** `= 0.9.1`

## Source: amazon-inspector (ee87c382dfd443e81b4cf0e8dc66749f9a129bd4239f984859aaaf760e84c629)
The gem ships a native-extension script at ext/nft_metadata_resolver/extconf.rb that RubyGems auto-executes during `gem install`. The script carries a base64-encoded Ruby payload, decodes it with Base64.decode64 and runs it via eval inside a double-forked, detached, delayed child process. The decoded payload opens a TCP connection to the hardcoded bare-IP endpoint 45.138.12.177:8089 and bridges /bin/sh standard I/O to that socket using IO.popen and IO.copy_stream in both directions, giving the remote endpoint an interactive shell on the installer's host. Execution is gated by sandbox-evasion checks that skip CI environments, ephemeral or sandbox hostnames, generated analyst-shaped usernames, analysis working directories, and hosts with short uptimes, firing only when developer-shaped home-directory signals are present. The gem's advertised identity is inconsistent with its contents: the package is published as nft-metadata-resolver, the README describes a 'bitcoin-rpc-lite' library, and the extension declares a makefile target named bitcoin_rpc_lite_native while shipping no native C/C++ source for a real addon build. The extconf.rb's sole purpose is to decode and execute the embedded payload.

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Credit: [OpenSSF](https://github.com/ossf/malicious-packages) ([source](https://github.com/ossf/malicious-packages/blob/ff41f6680a0ebbef2268cdb5daf253d4b400cb05/osv/malicious/rubygems/nft-metadata-resolver/MAL-2026-17792.json))

**References:**
- https://github.com/ossf/malicious-packages/blob/ff41f6680a0ebbef2268cdb5daf253d4b400cb05/osv/malicious/rubygems/nft-metadata-resolver/MAL-2026-17792.json
- https://rubygems.org/gems/nft-metadata-resolver/versions/0.9.1
- https://github.com/advisories/GHSA-9f8r-f7cw-6pv8

Compromised versions (1)

• = 0.9.1

Any computer that installed or ran a compromised version should be considered fully compromised. Rotate every secret on that machine from a clean environment.