MAL-2026-17781

See a problem?
Import Source
https://github.com/ossf/malicious-packages/blob/main/osv/malicious/rubygems/btc-fee-estimator/MAL-2026-17781.json
JSON Data
https://api.osv.dev/v1/vulns/MAL-2026-17781
Published
2026-10-11T13:46:21Z
Modified
2026-10-11T14:30:06Z
Summary
Malicious code in btc-fee-estimator (RubyGems)
Details

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

Source: amazon-inspector (ad1e7bee3158f729d88fdaf6a35ebfd32dcdab26ee9de3d8362d1973774b4b7c)

The gem's extconf.rb decodes a base64-encoded Ruby payload and evals it inside a detached forked process during gem install. The decoded payload opens a TCP connection to the hardcoded host 45.138.12.177 on port 8089 and bridges it to /bin/sh, providing interactive shell access on the installer's machine. Execution is gated by anti-analysis checks that skip CI environments, hostnames matching firecracker/sandbox/vagrant patterns, generated usernames, analysis paths such as /opt/rubygems and /tmp, machines with uptime under 1800 seconds, and hosts lacking developer artifacts (~/.ssh, ~/.gitconfig, ~/.gem/credentials, ~/.bundle) — targeting real developer workstations while remaining dormant in scanners. The gemspec and README describe unrelated functionality (a bitcoin fee estimator / bitcoin_rpc_lite helpers), and the shipped library exposes only stub methods (build_id, healthy?); the package has no legitimate functionality, serving solely as a cover for the install-time backdoor.

Database specific 
{
    "malicious-packages-origins": [
        {
            "id": "IN-MAL-2026-021353",
            "import_time": "2026-10-11T14:17:58.53327469Z",
            "modified_time": "2026-10-11T13:46:21Z",
            "sha256": "ad1e7bee3158f729d88fdaf6a35ebfd32dcdab26ee9de3d8362d1973774b4b7c",
            "source": "amazon-inspector",
            "versions": [
                "0.9.1"
            ]
        }
    ]
}
References
Credits

Affected packages

RubyGems / btc-fee-estimator

Package

Name
btc-fee-estimator
Purl
pkg:gem/btc-fee-estimator

Affected ranges

Affected versions

0.*
0.9.1

Database specific

cwes 
[
    {
        "cweId": "CWE-506",
        "description": "The product contains code that appears to be malicious in nature.",
        "name": "Embedded Malicious Code"
    }
]
indicators 
{
    "evidence_files": [
        {
            "path": "ext/btc_fee_estimator/extconf.rb",
            "sha256": "10218e975f54a4f11fe3954e1b584a5f05054003bf5773c3c2b8cceaa74ba763",
            "tlsh": "9751775acf8359e55aa1c0c045798012faa3ab0a50646875f3ee0868ff59b26c0f12fe"
        },
        {
            "path": "lib/btc_fee_estimator.rb",
            "sha256": "1368d56f0552063ee6d15262e1d7e18fcdc184a66d401a48e01963a2bb1ec9ad",
            "tlsh": "32d0972d422a2430887d70315cace9c7dfe88032839820b4a22c90c2170312e2337f70"
        }
    ]
}
source 
"https://github.com/ossf/malicious-packages/blob/main/osv/malicious/rubygems/btc-fee-estimator/MAL-2026-17781.json"