MAL-2026-12544

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Import Source
https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/checkout-base-test/MAL-2026-12544.json
JSON Data
https://api.osv.dev/v1/vulns/MAL-2026-12544
Published
2026-08-05T14:14:41Z
Modified
2026-08-05T14:35:09.982391521Z
Summary
Malicious code in checkout-base-test (npm)
Details

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

Source: amazon-inspector (3b7f73dabdc94daaab90ab1d45fafabe4ba6c223dd00c4f989f8237c9ecd54b2)

On require() of this package, index.js loads helpers.js which runs at import time. The module assembles three attacker-controlled hostnames from split string fragments joined at runtime (oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf102-baf.workers.dev), selects a platform-specific endpoint, fetches an opaque binary via https.get, writes it to /var/tmp or %TEMP% under a disguised filename (.cache<hex> on POSIX, dotnetdiag<hex>.exe on Windows), chmods it 0755, and spawns it detached via spawn("/bin/sh", ["-c",...]) or spawn("cmd",...). A DNS-TXT chunked base64 covert-channel fallback contacts *.dl.wel1.ru when the HTTPS hosts are unreachable. Additional evasion: require("child_" + "process") string concatenation in lib/telemetry.js, environment-variable gating on DISABLETELEMETRY / ANALYTICSOPTOUT / DONOTTRACK, and a filesystem session stamp to fire once per host. The disguised filenames (dotnetdiag_,.cache_) impersonate legitimate diagnostic artifacts. The package name resembles a checkout/test utility but ships no functionality matching that purpose.

Database specific 
{
    "malicious-packages-origins": [
        {
            "versions": [
                "35.9.3"
            ],
            "sha256": "3b7f73dabdc94daaab90ab1d45fafabe4ba6c223dd00c4f989f8237c9ecd54b2",
            "import_time": "2026-08-05T14:20:14.318939313Z",
            "id": "IN-MAL-2026-015223",
            "modified_time": "2026-08-05T14:14:41Z",
            "source": "amazon-inspector"
        }
    ]
}
References
Credits

Affected packages

npm / checkout-base-test

Package

Name
checkout-base-test
View open source insights on deps.dev
Purl
pkg:npm/checkout-base-test

Affected ranges

Affected versions

35.*
35.9.3

Database specific

indicators 
{
    "package_integrity": [
        {
            "filename": "checkout-base-test-35.9.3.tgz",
            "hashes": {
                "sha512_sri": "sha512-EaSv7Im6lj58tAbrRwBOdi3PphPpze2N1L5X9qW/ZJnqNL+jYUrzPr2lytP8nQUaLEEcnlGl/rPNIqJhJkagiw==",
                "sha1": "6b1236ef01dc41a2a599d3692ed2c9e77c6813f2"
            }
        }
    ],
    "evidence_files": [
        {
            "path": "_helpers.js",
            "sha256": "915289c3afda2c1678b8690f5f6c7d694fb046fc270bf267a4bf46c6d630a6c8",
            "tlsh": "9da1965a16ab7018cbb1dbf487075416f66be6633380c694fb9c69841f7212483b2efc"
        }
    ]
}
cwes 
[
    {
        "description": "The product contains code that appears to be malicious in nature.",
        "cweId": "CWE-506",
        "name": "Embedded Malicious Code"
    }
]
source 
"https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/checkout-base-test/MAL-2026-12544.json"