Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true_CVE-2026-23986

{
    "lastseen": "",
    "description": "Copier is a library and CLI app for rendering project templates. Prior to version 9.11.2, Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use unsafe features like custom Jinja extensions which would require passing the `--UNSAFE,--trust` flag. As it turns out, a safe template can currently write to arbitrary directories outside the destination path by using directory a symlink along with `_preserve_symlinks: true` and a generated directory structure whose rendered path is inside the symlinked directory. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user's write permissions), e.g., to cause havoc. Version 9.11.2 patches the issue.",
    "published": "2026-01-21T22:20:37.720Z",
    "modified": "2026-01-22T16:49:26.426Z",
    "type": "cve",
    "title": "Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true",
    "source": "GitHub_M",
    "references": "https://github.com/copier-org/copier/security/advisories/GHSA-4fqp-r85r-hxqh\nhttps://github.com/copier-org/copier/commit/b3a7b3772d17cf0e7a4481978188c9f536c8d8f6\nhttps://github.com/copier-org/copier/releases/tag/v9.11.2",
    "id": "CVE-2026-23986",
    "bulletinFamily": "",
    "cwe": [
        "CWE-61"
    ],
    "cvelist": null,
    "sourceData": "copier-org copier < 9.11.2",
    "sourceHref": "",
    "cvss": {
        "score": 6.9,
        "severity": "MEDIUM",
        "vector": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N",
        "version": "4.0"
    },
    "cvss2": [],
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        "baseScore": 0,
        "baseSeverity": "",
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        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "copier",
    "version": "< 9.11.2",
    "vendor": "copier-org",
    "ai_description": "",
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    "ai_score": 0
}