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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-4fqp-r85r-hxqh Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 21 Jan 2026 22:30:00 +0000

Type Values Removed Values Added
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.
Title Copier safe template has arbitrary filesystem write access via directory symlinks when _preserve_symlinks: true
Weaknesses CWE-61
References
Metrics cvssV4_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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-01-21T22:20:37.720Z

Reserved: 2026-01-19T18:49:20.656Z

Link: CVE-2026-23986

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-01-21T23:15:52.793

Modified: 2026-01-21T23:15:52.793

Link: CVE-2026-23986

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses