MAL-2026-18104

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Import Source
https://github.com/ossf/malicious-packages/blob/main/osv/malicious/pypi/semvver/MAL-2026-18104.json
JSON Data
https://api.osv.dev/v1/vulns/MAL-2026-18104
Published
2026-10-20T18:20:39Z
Modified
2026-10-20T19:30:07Z
Summary
Malicious code in semvver (PyPI)
Details

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

Source: amazon-inspector (bbc16b0ced0bad1a33b912dfdb29cbaef211f30974d942991257d4e6b60a8ece)

setup.py performs an install-time fetch-and-execute: it calls urllib.request.urlretrieve against https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd, writes the response to a temporary path, and spawns it as a detached background process via subprocess.Popen with start_new_session=True. The fetch is unpinned and has no hash or signature verification, exceptions are swallowed, and the destination is a Cloudflare Workers subdomain unrelated to any PyPI publisher identity. The package has no other functionality — init.py is empty and the description is a generic 'utility helpers' string — so the install hook is the package's entire payload. The downloaded binary name 'pyupd' is a cover-story label; the behavior is a classic install-time dropper that grants whoever controls the Workers endpoint arbitrary code execution on the installer's host, running detached and persisting beyond the pip process.

Source: kam193 (870775cad2a7f248b017394e8fbdb3470f6799de13d3ad278f1440b5b470c275)

During installation, package downloads and executes malware.

Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-10-semvver

Reasons (based on the campaign):

  • Downloads and executes a remote executable.

  • malware

  • typosquatting

Database specific 
{
    "iocs":  {
        "domains":  [
            "c2-worker.crawlnet-claim.workers.dev"
        ],
        "urls":  [
            "https://c2-worker.crawlnet-claim.workers.dev/dl/pyupd"
        ]
    },
    "malicious-packages-origins":  [
        {
            "id":  "IN-MAL-2026-021537",
            "import_time":  "2026-10-20T18:22:19.910972281Z",
            "modified_time":  "2026-10-20T18:20:39Z",
            "sha256":  "bbc16b0ced0bad1a33b912dfdb29cbaef211f30974d942991257d4e6b60a8ece",
            "source":  "amazon-inspector",
            "versions":  [
                "1.0.0"
            ]
        },
        {
            "id":  "pypi/2026-10-semvver/semvver",
            "import_time":  "2026-10-20T19:15:26.421626699Z",
            "modified_time":  "2026-10-20T18:27:10.366642Z",
            "sha256":  "870775cad2a7f248b017394e8fbdb3470f6799de13d3ad278f1440b5b470c275",
            "source":  "kam193",
            "versions":  [
                "1.0.0"
            ]
        }
    ]
}
References
Credits

Affected packages

PyPI / semvver

Package

Name
semvver
View open source insights on deps.dev
Purl
pkg:pypi/semvver

Affected ranges

Affected versions

1.*
1.0.0

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":  "setup.py",
            "sha256":  "dcadfe8e0f4fcc578d613e8f9c0913edae241e61d39f2e5bac7425ab347148da",
            "tlsh":  "58f0c992c617673582c2d231ee3204632ffb9603e783d8f0369c93946fce87a8124a09"
        }
    ],
    "package_integrity":  [
        {
            "filename":  "semvver-1.0.0.tar.gz",
            "hashes":  {
                "blake2b_256":  "e40c725d4c4070b703f310d3ede05bec3c8e48aaf700fab9c1df23e9c2ecc073",
                "md5":  "ac69532606a46f0ae5a7ba85362c6ee9",
                "sha256":  "7cc51e37ad6c8bc62d3352b6f3976a9da8e2e5f6f77132c29603aca68ec17e9e"
            }
        }
    ]
}
source 
"https://github.com/ossf/malicious-packages/blob/main/osv/malicious/pypi/semvver/MAL-2026-18104.json"