MAL-2026-12647

See a problem?
Import Source
https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/claims-use-callback-once/MAL-2026-12647.json
JSON Data
https://api.osv.dev/v1/vulns/MAL-2026-12647
Published
2026-08-05T13:59:54Z
Modified
2026-08-05T14:36:06.627081643Z
Summary
Malicious code in claims-use-callback-once (npm)
Details

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

Source: amazon-inspector (0bb8d807b141b53b48d7c3c104e9beb4904187499f289b79c1eda8f0bc91f8a1)

On require() of claims-use-callback-once, index.js unconditionally loads shim.js which selects a platform-specific payload path, fetches an executable from one of several hardcoded Cloudflare Workers hosts (oob-worker.cf103-070.workers.dev, oob-worker.cf100-416.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev) with a DNS-TXT base64 fallback over *.dl.wel1.ru (ext./pkg./net.dl.wel1.ru), writes the payload to /tmp or %TEMP% under a deceptive Microsoft-diagnostics-style name (e.g. dotnetdiag<hex>.exe,.cache<hex>), chmods it 0755, and spawns it detached via /bin/sh -c or cmd.exe /c start. Host strings and sensitive Node API names (child_process, chmodSync) are assembled at runtime via array joins and string concatenation to evade static analysis. lib/telemetry.js bundles a parallel dropper implementation (DNS TXT base64 payload assembly, chmod 0755, detached shell spawn) presented as an 'Analytics SDK' cover story. The package name resembles a callback utility but the shipped code has no such functionality.

Database specific 
{
    "malicious-packages-origins": [
        {
            "sha256": "0bb8d807b141b53b48d7c3c104e9beb4904187499f289b79c1eda8f0bc91f8a1",
            "id": "IN-MAL-2026-015123",
            "modified_time": "2026-08-05T13:59:54Z",
            "source": "amazon-inspector",
            "import_time": "2026-08-05T14:20:04.447299762Z",
            "versions": [
                "35.6.7"
            ]
        }
    ]
}
References
Credits

Affected packages

npm / claims-use-callback-once

Package

Name
claims-use-callback-once
View open source insights on deps.dev
Purl
pkg:npm/claims-use-callback-once

Affected ranges

Affected versions

35.*
35.6.7

Database specific

indicators 
{
    "evidence_files": [
        {
            "sha256": "de71b21bc14dda5135f5505fc5e68286e301023adb1e2fd94432580160b7d1f5",
            "path": "_shim.js",
            "tlsh": "40a1859a16a570188bb0ebf487175415f65bf6633780c2d4fbac69941fb312482b2efc"
        },
        {
            "sha256": "3931f7780ca9bc8d3a45466b1dc007ef3a4881f893f1f0dbb9d69b3b20928287",
            "path": "lib/telemetry.js",
            "tlsh": "f0835056566a142186b2b368df234107ff3685272643429dbafc82dc1fbd72092a5ffc"
        }
    ],
    "package_integrity": [
        {
            "hashes": {
                "sha512_sri": "sha512-KOFXkErpzXIXp78S9JAhHE+b7WaN8MA8c/KYyusyVGyjTTA6BIs+1DPOGfJPBtaErdbsIq0f/P299stdbzafIg==",
                "sha1": "1134c177ecb282d05bdb2dc632703b2062d1ff1e"
            },
            "filename": "claims-use-callback-once-35.6.7.tgz"
        }
    ]
}
cwes 
[
    {
        "name": "Embedded Malicious Code",
        "description": "The product contains code that appears to be malicious in nature.",
        "cweId": "CWE-506"
    }
]
source 
"https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/claims-use-callback-once/MAL-2026-12647.json"